With Nigel being out of his element through the documentary and him meeting some of the biggest and most dangerous marine animals known in the fossil record, this series it's thalassophobia incarnated.
- The main theme is very dark and ominous, which fits as Nigel frequently goes into dark, murky waters almost entirely unprotected.
- The build-up to the Orthocone as the star attraction of the first segment is effective, and the revealing shot with ominous music is effective.
- The scene where the Cymbospondylus are circling Nigel and testing before attacking is appropriately tense.
- The Dunkleosteus is large, vicious, and eager to break open Nigel's diving cage. As Nigel puts it, he feels extremely vulnerable and it's strongly implied the cage would not have survived a prolonged attack. The cliffhanger of the first episode has a P.O.V. Cam of Nigel as the Dunkleosteus barrels right towards him. When the action resumes in the next episode, there is a frightening "thunk" as it bangs into the cage, denting it like a can of soda. To top it all off, the Dunkleosteus, when unable to eat Nigel, goes and eats a young member of its' own kind.
- The Eocene segment spends a lot of time building up the Basilosaurus, with Nigel's crew using ominous whale calls to try to summon it to the Ancient Mariner.
- The Megalodon segment also uses a lot of suspenseful build-up to the unveiling of the massive shark, and the cliffhanger of this episode ends when the Megalodon seemingly eats Nigel.
- In the Jurassic segment, the climax takes place at night when there's little light, and Nigel watches a swarm of Liopleurodon eating a dead Leedsicthys. It's tense, alarming, and Nigel is only barely saved by his chemical deterrent. Even when the segment ends and Nigel begins leaving the sea, the narrator ominously warns that now he must face the deadliest sea of all time.
- The Cretaceous sea is dubbed "Hell's Aquarium", and is so dangerous that Nigel refuses to go into the water at first. Sure enough, he nearly pays the price when a Mosasaurus attacks his boat when he decides to go swimming with an Archelon anyway.
- The end of the show has one hell of a Bolivian Army Ending, in which the crew is asleep at night, only for the radar to begin ominously picking up a bogey, first one, then several, then an entire horde of Mosasaurus. Considering the size of the biggest ones, it's safe to say they are more within the capability of taking down the Ancient Mariner and devouring her crew.
