* AlternateCharacterInterpretation: The WebVideo/GameGrumps posit that Alfred Thorman is an obsessed, passive-aggressive old man who fumes to himself when he doesn't get results from his e-mails to the player while hiding behind his "TakeYourTime" presentation.
** The dear Grumps also take Kat's offhand 'it gets kind of lonely up here' comment and interpret her as an extremely aggressive lesbian.
* CriticalResearchFailure: In 2, you find quite a lot of the lapis lazuli stone underwater with the explanation that a ship sank there in the earlier 20th century carrying a cargo of it. The only problem is that lapis lazuli ''dissolves'' in water.
* CrowningMusicOfAwesome: ''Blue World'' exclusively features tracks by Music/CelticWoman, and there's one for most every area of the game. The songs fit the tone and environment of each area perfectly. YMMV because the somewhat cloying and schmaltzy nature of the songs could be {{Narm}} or NarmCharm for some players.
** Some of the in-game soundtrack is very nice and soothing, particularly the Valka Castle theme.
** The original uses Hayley Westenra's "Prayer", and the player can use an SD card to play their own AwesomeMusic when they dive.
* EvenBetterSequel: ''Blue World'' addresses several complaints about the first ''Endless Ocean'' and sacrifices very little in the process.
* LesYay: While romantic tension between the player and Kat/Oceana is kept pretty minimal and vague, the dialogue is the same whether the player is male or female.
* NightmareFuel: [[spoiler:The FinalBoss of ''Blue World'', two]] Goblin Sharks [[spoiler:and the Okeanides Guardian. ''Dear god'' the Guardian. It's even implied in-game that the Okeanides people selectively bred it to be scary! (though how they got the phenotype to stay dominant in the goblin shark population without intervention for thousands of years is a mystery).]]
** [[NightmareFuel/EndlessOcean The game has a surprising amount of this.]]
* SweetDreamsFuel: [[https://www.youtube.com/watch?v=IsY0TyUrq98 "Prayer"]].
* TearJerker: [[spoiler:Kat's backstory]], and the secret cutscene unlocked by sitting on the deckchair at sunset.
** And then, in ''Blue World''... [[spoiler:Jean-Eric's son (and Oceana's father) Matthias became trapped in his submersible 650 feet down in the Zahhab Depths while researching the Song of Dragons; he died attempting to escape and left a message for his father in a waterproof case explaining why his work was important to him and that he loved his family very much, giving his old man something to shoot for once more.]]
** [[spoiler:Sidequests heavily imply that Matthias is still alive but the plot thread is never fully resolved.]]
* ThatOneBoss: [[ThreateningShark Thanatos]] shows up once in the main storyline and a few times in other quests. He's immune to the pulsar gun and needs to be avoided or fled. No so easy when you have to search his area for a salvageable.
** Even worse on one particular side quest, where you have to distract Thanatos and keep him away from another diver. Unless you're good at dodging, you're going to lose a lot of air.
* ThatOneLevel: Ciceros Strait. It's swarming with sharks and whirlpools. The whirlpools block off a section of the map during the day, so you have to go there at night - and put yourself at risk of running into Great White Sharks or Thanatos, who tend to lurk around wrecks with salvageables around them.
* ThatOneSideQuest: In ''Blue World'', making one million dollars [[spoiler: to excavate the Okeanos temple]] after you complete the main story. Most jobs you take that even reward money and not equipment pay a couple thousand at best, so you have to spend several tedious hours do some same jobs over and over again. There's no hint of this quest coming up, so if you've been spending all the money you've earned so far on other things you're screwed.
** The game then pulls a rather annoying fast one on you: turns out you can reopen the temple for ''half'' that, but the option still isn't available until you've gotten the full $1 million. The result being that you can then purchase pretty much all the best equipment and the items for Nine-Ball Island at once after the temple's been opened, which is nice, but many players will probably still feel annoyed about the FakeLongevity.
* TheyChangedItSoItSucks: A minor example, but many players were flummoxed and annoyed by ''Blue World'' removing the option to play custom music from an SD card. There is a jukebox you can purchase that will play music during dives, but it only has the Music/CelticWoman tracks previously heard in the story.
* UglyCute: Lots of the fish are pretty in really bizarre ways.
** Even an InUniverse example, as Oceana squeals over many of them.
* TheWoobie: [[spoiler:Kat.]]