* The whole ''situation''. There are plenty of historical records (and a couple of modern incidences such as detailed in ''Film/ThePerfectStorm'') that suggest rogue waves like this do exist and have sunk ships. Rather like the movie, as well, there'd be few if any survivors from such a sudden and catastrophic event - and those few survivors would probably have been washed clear and likely very badly injured to boot. Not to mention if you were trapped inside a ship the size of the Poseidon when it turned turtle, it would probably sink long before you got to an opening.
* The sequence of the wave hitting. Modern cruise ships are often described as "a city on the waves." Now imagine a city ''turning over'' on its side and then upside down.
** A shot underwater shows corpses floating by still in evening dress.
** One unfortunate passenger is sent flying out of the glass elevator back into the ballroom below. Her desperate wailing is especially unsettling.
** One group of passengers were enjoying themselves in the ship's pool when they suddenly find themselves being washed away before the real wave even enters the room, then being swept out along with the pool's windows (and the pool water itself) when the ship rolls over.
** An explosion causes a kitchen hallway to fill with fire, the workers seeing it coming but unable to run before they're burned alive.
*** Even worse, when Dylan and co. happen upon their bodies much later, they note how the superheated air from the flash fire would have cooked their lungs from the inside out.
* The gathered survivors in the ballroom watch in horror as the "watertight windows" slowly crack under the unrelenting pressure. Panic builds as they realize what's going to happen, and there is no way to escape (as all of the watertight doors that were sealed earlier and the only way out of the room have now flooded). As everyone in the room begins to run around and scream in panic, the singer tearfully walks towards the captain as they prepare to face the inevitable and simply hug each other. The windows shatter and water floods the room, killing everyone.
** Above the ballroom, the surviving group stands silently and somberly listens to the people's screams as they all drown. You can almost tell how much they wish they could've done more to help, but now that the ballroom – the ''only'' room that held survivors – has been flooded, the group is devastated with the fact that they've crossed the PointOfNoReturn and now there's no one left to save but themselves.
* The entire air duct scene. It's dark, cramped, and slowly being flooded with water. And if Conner hadn't managed to get the vent cover off, everyone in the duct would have been trapped, knowing they were going to die, and not being able to do anything about it as the water slowly rose and drowned them one by one--Dylan's increasing panic as the water steadily rises over him is especially terrifying.
* Creator/KurtRussell does a ''frighteningly'' good job of portraying someone who's drowning.
* The elevator shaft. Enough said.
** Especially how Valentin dies.
* The ship righting itself during its final plunge, now a complete 180 from the majestic vessel we first saw--broken, shattered--and finally sinking into the depths of the sea, taking any scant survivors with it. The ship even lets out a loud groan as it sinks, as if it were crying out in pain.
* ''Everyone'' in the upturned disco getting electrocuted to death as Jennifer and Elena watch and hug each other in horror.
* The way in which Elena dies, snagging her skirt on an errant wire when swimming underwater at the tail-end of the survivors. Made even more horrifying by the fact that she was already claustrophobic and was convinced that she was going to die not 10 minutes earlier, making her previous escape short-lived. Although she's spared the pain of drowning by knocking herself unconscious, and the others do their utmost best to revive her, her last moments are of sheer distress and abandonment from the rest of the group. Adding it as {{Tearjerker}}, she was only on the ship to see her younger and ill brother, having snuck on illegally just to do so. Dylan used getting to see him as motivation for her to calmly escape the air vent, saying how she wouldn't want him to think she never came for him. This makes her death all the more heartbreaking.

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