Perilous Prehistoric Seas

Art by Luis V. Rey.

"Why is the [Cretaceous Niobrara Sea] more deadly than the others? It's because there's not just one predator here, there's a whole suite of them. There's frightening sharks, terrifying sea reptiles, even the fish in here you couldn't imagine in your worst nightmares. I call this Hell's Aquarium, it's so jam-packed with killers."

— Nigel Marven, Sea Monsters

The world of prehistoric life is a fascinating one, teeming with all sorts of bizarre, unique, and otherwordly creatures that vanished millions of years ago. This, coupled with the fact that many were gigantic, means they are a vivid source of imagination for many and various interpretations can be made out from them.

While the dinosaurs are undoubtedly the most famous (and most favored) prehistoric creatures, that's not to say that life in the seas was any less mysterious than its terrestrial counterpart. If anything, the underwater realms of the prehistoric world are arguably more mystique and otherwordly than the dinosaurs, its predecessors in the Paleozoic, and the Age of Mammals of the Cenozoic; this may have something to do with our perception and knowledge of the oceans and their fauna.

Our general understanding of prehistoric life in seas and oceans is just as unclear and speculative as it is of the dinosaurs and the Ice Age, with the additional fact that we are not as well-versed about underwater life as we are about terrestrial life. Based on fossil evidence, much of what has been uncovered and studied have been known to look ferocious and most likely predatory in nature, such as the mosasaurs of the Mesozoic and the legendary shark megalodon of the Cenozoic. While not as common as stories about dinosaurs, there have been a number of works that have placed focus on these animals, usually being depicted as deadly beasts who reigned the seas as apex predators. On other occasions, less frightening sea creatures of prehistoric times have also been depicted, being seen struggling to adapt and survive in a hostile environment filled with predators on all sides.

This trope frequently involves Artistic License – Paleontology, given that, as mentioned above, our knowledge of prehistoric life is based on evidence collected and studied by paleontologists and speculative reconstructions of their appearance and behavior. On another note, because sea life is generally harder to describe and understand than terrestrial life, moments of Shown Their Work are a lot harder to come by here.

As detailed above, this trope has a lot of overlap with Prehistoric Monster, Sea Monster, and Hazardous Water, although there are more sympathetic perspectives added to the trope, provided the narrative's main focus is on a creature whose habitat is the sea and is trying to find a way to survive. Also compare Death World if certain depictions of the seas are unrelentingly brutal in comparison to other examples. Given that most of the creatures of Prehistoric Seas were either carnivores or piscivores, Always a Bigger Fish is a common occurrence and also potentially serves as a demonstration of how little land animals stand a chance against such threats when out of their element. Can also overlap with Ocean of Adventure, especially if the main focus is on a marine animal.

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Examples

Art

• One artwork◊ by famed paleoartist Charles R. Knight shows a Tylosaurus pursuing a pair of fish at what appears to be high tide. The art does a good job of establishing Tylosaurus as a predator, with its design in the artwork being very evocative of it being a prehistoric Sea Serpent.
• Having had a prolific history as a paleoartist, Luis V. Rey is no stranger to prehistoric marine life. One of them shows a Tylosaurus pair trying to attack a Quetzalcoatlus ^note  A bit of Artistic License – Paleontology, though, since Quetzacoatlus has since been established to be more of an inland dweller. This particular artwork has been used as the book cover for a book called Prehistoric Monsters.
• A popular early paleoart trope in the 19th century was nightmarish scenes of prehistoric sea creatures battling each other◊ in a dark, tumultuous ocean. As paleontology progressed and artistic tastes changed, painters like Zdeněk Burian would recapitulate similar scenes in much more naturalistic presentations◊, usually with the peril more implicit but still present.

Documentaries

• Amazing Dinoworld: The second episode, The World of Sea Monsters has Mosasaurus as the main focus. The episode emphasizes Mosasaurus as a fearsome apex predator (it's even shown killing a Tyrannosaurus rex) whilst also having to deal with the hardships of ocean life, such as struggling to catch prey, finding a mate, etc. And that's not to mention competing against other mosasaurs either.
• Dinosaur Planet: While the seas of the Late Cretaceous aren't given focus, the episode, Pod's Travel shows that the titular Pyroraptor didn't have a pleasant trip to Hateg Island as the seas did claim the life of one of his sisters during a storm and the other sister was caught and dragged underwater by an elasmosaurid. Stranded on a log with no available food for three days in the middle of the seas left Pod bereft of food and nourishment, at least until he landed on Hateg Island as a stowaway.
• Dinosaur Revolution: A Tylosaurus gives birth to live offsprings... until a shark suddenly appears and eats up all but one of them. The tylosaur proceeds to eat the shark in revenge. It shows that while formidable predators, tylosaurs are still animals that depend on their offspring to carry on.
• Monsters Resurrected: The second episode, T. rex of the Deep is centered around how and why Tylosaurus was the apex predator of the Late Cretaceous seas. The mosasaur is depicted as being able to hunt up to anything it could catch with its jaws, including others of their own kind. The episode also features other creatures like Styxosaurus, Dolichorhynchops Cretoxyrhina, and Xiphactinus who are shown to be struggling to survive in their environment.
• Planet Dinosaur: The episode Fight for Life has segments dedicated to life in the seas of the Jurassic period, revolving around the marine reptile Kimmerosaurus, which hunted small sharks like Squatina but was preyed upon in turn by the much larger plesiosaur Pliosaurus ^note at the time, it was known provisionally as "Predator X". The former can take refuge in shallow water, but must venture into the deeper ocean for feeding, where it is vulnerable for predation by Pliosaurus, which uses its greater size and power along with its marginally higher speed to overwhelm its prey. The episode closes off with the narration noting that the odds were always in the predators' favor in the struggle for survival, and that Pliosaurus ""ruled the oceans for more than 100 million years."
• Prehistoric Planet: The episodes Coasts and Oceans place significant emphasis on the oceanic residents of the Cretaceous Period, with each of them displaying their lifestyle and struggles.
  • Mosasaurus is depicted as an apex predator, but the particular focus is on an older male who struggles to find food and has to battle against a younger rival to ensure his own survival as well as needing its teeth cleaned by fish to make sure they're on good condition.
  • Tyrannosaurus ends up on the receiving end of the trope; a father tries to lead his young to a nearby island to find food. However, because they are crossing through a path where they are not adapted to defending themselves properly, the infants are easy prey for a passing Mosasaurus who ends up eating some of them before the tyrannosaur family makes it to shore.
  • A pregnant Tuarangisaurus is also given focus, trying to find food to keep herself nourished as well as finding a safe spot to give birth to her young. She is attacked by a Kaikaifilu as her pregnancy leaves her unable to swim at her normal pace and become exhausted quickly. Luckily, her pod drives the Kaikaifilu away after which the Tuarangisaurus gives birth.
  • The ammonites are a comparatively mundane example; they participate in a grand mating ritual, but all the adults die shortly after giving birth with the younglings having to scour around the seas on their own in the hopes they can survive to adulthood without getting eaten.
• Prehistoric Predators: While mainly focusing on the terrestrial predators of the Cenozoic, it also dedicates an episode to megalodon, exploring how big it could have gotten, how it would have looked like, and how it hunted various prey items (from sea cows to giant baleen whales) and dominated our oceans for millions of years until its extinction in the Pliocene. It also features the much smaller toothed whale Squalodon, presented as a rival species that uses its higher intellect and Zerg Rush to combat the megalodon's sheer size and strength, with paleontologists comparing it to today's orca.
• Sea Monsters A Prehistoric Adventure: This documentary is set in the Western Interior Seaway 82 million years ago and focuses on a young female Dolichorhynchops, chronicling her life from her birth to her death. She is threatened by the various predators of the inland sea, including Xiphactinus, Cretoxyrhina, and Tylosaurus.
• Sea Rex Journey To A Prehistoric World: This documentary focuses on apex predators who lived in the seas during the Mesozoic Era, including Tylosaurus, Mosasaurus, Kronosaurus, and Shonisaurus. The documentary delves into how they evolved into being the best predators in their environments, but they are also stated that they have just as many perils and challenges to contend against and aren't invincible.
• Walking with…:
  • Walking with Dinosaurs: The third episode, Cruel Sea is entirely set on the shores of Late Jurassic England, showcasing just how much of a danger the seas could be. Best shown when a (massively oversized) Liopleurodon suddenly rises up to scoop a fishing Eustreptospondylus and drag it underwater to devour it. That said, the episode focuses on an ichthyosaur known as an Ophthalmosaurus where several young are trying to make an effort to survive and the hardships that come with it, including having to deal with underwater predators like adults of its own kind and the aforementioned Liopleurodon.
  • Walking with Beasts: The second episode, Whale Killer takes place in Late Eocene, Pakistan. The central animal, Basilosaurus is the Tethys Sea's apex predator, inspiring fear towards all other aquatic life, though infants and juveniles are still in danger of being preyed upon. The focus of the episode is on a pregnant Basilosaurus soon to give birth and her struggle in trying to catch prey, showcasing that the prehistoric seas are a hard life, even for apex predators.
  • Sea Monsters naturally is about these, from giant sea scorpions and cephalopods in the Ordovician period to mosasaurs of the Niobrara Sea (more commonly known as the Western Interior Seaway) in what's dubbed the Deadliest Seas of all time. Many of the creatures that Nigel encounters are actually quite docile, or at least uninterested in attacking him, and are more concerned with their own needs. While there are genuine threats like the megalodon, Liopleurodon (again, much larger than life), and the Tylosaurus, this only ends up being the case whenever Nigel gets too close to them, otherwise, they are only hunting for their preferred prey and react in a way any other animal would. That said, in the end, a Tylosaurus family does cross into Prehistoric Monster territory by approaching and attacking Nigel's ship.
  • Walking with Monsters: Ocean Killers is mainly centered on the oceans of the Paleozoic era and how its fauna lived and survived. One example is that trilobites are seen as fragile creatures under the mercy of the Houcaris^note then known as Anomalocaris in the Cambrian.

Fan Works

• Prehistoric Park Reimagined: The prehistoric oceans that the rescue team travels to for the sake of rescuing prehistoric aquatic animals prove to be very dangerous locations with suitably dangerous residents:
  • In season one episode Devils of the Deep, the rescue team travels to the Gogo Reef in the days of the Devonian period. During this mission, an Onychodus almost bites an arm off of Leon, a Titanichthys comes rather ominously close to colliding with Leon and Jack while they're distracted with an argument, and a foursome of Dunkleosteus come scarily close to maiming or killing team leader Drew.
  • In season two episode Sea Serpents, the rescue team rescue Eocene wildlife from both the terrestrial and marine side of the environment. And over the course of their adventures out on the ocean, the rescue team manages to encounter several dangerous sea life, with the climactic final rescue of the episode involving the rescue team protecting a pod of Zygorhiza that are in the midst of birthing from getting hunted and eaten by a combined group of basilosaurus, the shark Otodus angustidens, and a newly discovered giant species of choristodere called dracosuchus.

Films — Animated

• Fantasia: Tylosaurus appears in the Rite of Spring section, where they are pack hunters. They're shown hunting and killing a Pteranodon when one makes the unfortunate decision of descending too close to the waters.
• The Land Before Time: While aquatic creatures, such as Elsie the Elasmosaurus in The Mysterious Island have made brief appearances, the ninth film, Journey to Big Water places them on central focus, namely an Ophthalmosaurus named Mo, who befriends Littlefoot as a blood brother, and an antagonistic Liopleurodon. The titular "Big Water" is really the sea, which Mo wants to return to as his family is really there, and while the Liopleurodon is a massive threat, it only attacks Mo and The Gang of Five because they're nearby food, is starving to a lack of preferred prey, and is stranded in a lake.
• Speckles: The Tarbosaurus: The final battle between Speckles and One Eye takes place at an ocean cliffside. Then the fight is taken to the waters when One Eye knocks Junior into the sea and Speckles knocks him there in retaliation. Both the Tarbosaurus and the Tyrannosaurus start to fight in the waters, with neither of them being able to perform to their fullest extent due to being terrestrial predators. And to make matters worse, a Tylosaurus pair takes notice, though fortunately, they end up killing One Eye. Even then, because of exhaustion and not someone who adapted to an aquatic lifestyle, Speckles could barely swim to the nearest shores with Junior held in his jaws.

Films — Live-Action

• Journey to the Center of the Earth (2008): Whilst exploring the titular Center of the Earth whose wildlife consists of mainly extinct creatures, Trevor, Sean, and Hannah are forced to cross an underground sea. They're caught in the middle of a rainy thunderstorm and are forced to deal with a swarm of Xiphonactis. Fortunately, the Xiphonactis themselves have a predator, that being the Elasmosaurus who show up to devour the fishes, indirectly saving the trio.

Literature

• Animorphs: When sent back to the Cretaceous, Rachel ends up swallowed by a Kronosaurus and morphs into a grizzly bear to claw her way out.
• Destroyermen is set in an Alternate History version of the 1940s in which the K-T extinction never happened, resulting in a Death World that has many prehistoric elements, including extremely hostile seas. The most common dangers are swarms of voracious flasher fish, aggressive plesiosaurs called gri-kakka, and huge carnivorous whales called mountain fish (or leviathans) that can easily devour entire ships. It's implied that these hostile seas are the reason the world is (at least initially) a Points of Light Setting.
• Journey to the Center of the Earth: There is a strange, modern example depicted in the book known as the Lidenbrock Sea, which is located deep underneath the Earth. It is teeming with ravenous prehistoric creatures of the Cretaceous like ichthyosaurs and plesiosaurs and the main trio is forced to travel across the seas in their efforts to further explore the center of the Earth whilst having to bear all sorts of threats as well as the sight of a plesiosaur and an ichthyosaur fighting against one another.
• The New Dinosaurs: An Alternative Evolution: Taking place after the Mesozoic Era, but the asteroid not hitting the Earth, marine reptiles continued to evolve alongside the dinosaurs. Ammonites have become more predatory with the appearance of the Kraken which attacks with poisonous barks. Plesiosaurs and pliosaurs remained dominant predators in the oceans like the Birdsnatcher, Pelorus, and Pterosaurs like the Soar also prey upon Ammonites like the Kraken to make the latter's role more challenging. That said, Soars also falls prey to Birdsnatchers.
• Quintaglio Ascension: Subverted; while the setting takes place millions of years after the Mesozoic Era and in a setting where dinosaurs still thrived, the descendants of the Ichthyosaurs (Fish Lizard) and Plesiosaurs (Water Serpent) are actually hunted and fought by the titular Quintaglio who visit the seas with the intent of fishing the former for their own dietary needs. One Water Serpent, Kal-Ta-Goot, is the object of vengeance for Val-Keenir as it bit off his tail, but even that doesn't get much attention.

Live-Action TV

• Dinotopia: Subverted in a strange way; the series takes place on an idyllic island, though carnivores do remain territorial. The closest the series gets to a marine reptile is a territorial Mosasaurus pack, except they are more crocodilian-like in appearance and they dwell near water bodies like lakes and waterfalls. They attack the protagonists only because they intruded on their territory, but otherwise, they just mind their own business.
• Primeval: In Season 5, ARC members Connor, Abby, and Matt are sent to investigate a military submarine that has supposedly been intruded on by a creature, later revealed to a theropod. However, the submarine ends up being led into an anomaly, transporting them back to the Jurassic where they are under threat by a pod of Liopleurodon who develop a sort of curiosity towards the submarine before they consider attacking.

Video Games

• ARK: Survival Evolved: The setting of the game seems more contemporary, yet primordial, filled with what appears to be modern iterations of prehistoric animals like dinosaurs. Most of the ones that dwell under the seas include Basilosaurus, Coelacanth, Ichthyosaurus, Liopleurodon, megalodon, Mosasaurus, and Plesiosaurus. While all of them can be tamed, their behavior in the wild varies; some like Coelacanth are docile, while others like Basilosaurus, Plesiosaurus, and even Liopleurodon are more curious in nature unless provoked. Still, there are those that act aggressively upon notice like Mosasaurus and megalodon and are likely to make traversing through the waters difficult unless you're well-prepared and leveled.
• Dino Crisis:
  • Dino Crisis 2 is set in a world where a portion of the Cretaceous Period is displaced into the future due to tampering and overestimated research on 3rd Energy. As a result, an underwater facility became the swarming spot of packs of Mosasaurus and Plesiosaurus who proceed to kill off any divers and researchers they come across. Dylan and Regina also end up battling against a pack of Plesiosaurs and Pteranodon on their way to the facility via their boat. Regina herself discovers that the underwater section of the facility has been taken over by Mosasaurs who have killed all of the facility's workers there as well as a Plesiosaurus who thrives in the 3rd Energy Reactor as its territory. As usual in the franchise, both creatures act akin to Prehistoric Monsters.
  • The third level of Dino Stalker has Mike Wired travel on a boat to reach his designated spot of reaching a 3rd Energy Facility. Along the way, he has to battle against swarms of Plesiosaurs and Mosasaurs.
• Ecco the Dolphin and its sequel have prehistoric levels. There are Dunkleosteus, trilobites, and prehistoric jellyfish enemies as well as alien enemies, but the Pteranodon in Ecco: The Tides of Time helps Ecco by carrying him over obstacles too high to jump over.
• Roblox: The Dinosaur Simulator playthrough allows players to access the seas and even play as aquatic animals such as Mosasaurus, Ichthyosaurus, Elasmosaurus, Pliosaurus, and even megalodon. Given the nature of the game, players are expected to hunt for other aquatic creatures in order to survive as well as avoid being hunted down by other predators.
• Saurian: While the game is primarily set in the Hell Creek Formation, there is a coastal section of the map that leads to the Western Sea Interior. However, venturing into seawater for too long results in instant death as there would be a Mosasaurus waiting to target and devour you. The developers programmed this in case players become too curious to venture outside the given map.

Web Original

• Spec World: In a hypothetical world where dinosaurs and other extinct animals lived, mosasaurs continued to evolve and compete against one another with species like the Gigantoserpens and the "Nile Mosasaur" (Apep aegyptianus). It is said that the seas underwent several changes, which caused ocean-dwellers to undergo an "overdrive" regarding their evolution. Mosasaurs would eventually evolve into "Lizardwhales" and while larger, their diet changed to smaller creatures like giant cephalopods and small fishes. Hesperornithoforms like the many forms of Seaguin inhabit and swim across the Arctic Ocean, catching fish, though their small size makes them susceptible to being prey to other animals and rely on their agility to escape and fend for themselves.

Western Animation

• Primal (2019): The Season 2 premiere, Sea of Despair has Spear and Fang having to build a raft set off to the seas in their quest to save Mira. Along the ride, Spear and Fang have to hunt for food, which comes under the form of the turtle Archelon. While hunting the turtle isn't too hard, given that Spear and Fang are experienced hunters by that point, they are soon forced to contend against threats that they're not comfortable going up against, such as a Liopleurodon, a flock of Tropeognathus, and a megalodon.

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