Other mistake: When the survivors are in the funnel, there seems to be an explosion that comes from under them. Since the deck they were on was flooding, all the decks below would have been flooded. Whatever explosion that would've occurred in the funnel would have come from above, where whatever machinery was left would've caused it.
Other mistake: The stuntman who plays the telegraph operator, who drowns when the wave strikes, is also seen among the survivors in the dining room.
Other mistake: The dining room was filling up way too fast from the amount of water pouring in from the breach on the wall.
Other mistake: In the scene in the engine room, a steam pipe bursts and sprays hot steam (you can see the rising mist) on the handle of the door to the propeller shaft. After the steam has been off, Borgnine then grabs it with abandon. It should have burned his hand.
Other mistake: There was no way the dining room could have filled up with that much water in that amount of time.
Other mistake: In the scenes bookending the underwater swim, there is no way to figure out how both pools of water are set up. Sometimes a cast member jumps in and appears to be standing in 3 feet of water and other times cast members dive in as though the water is 25 feet deep. In fact, the whole underwater scene makes no sense at all. Cast members swim up meaning they're going through a hatch in the ceiling or floor, there are railings attached willy-nilly and there appears to be no regular doors anywhere.
Answer: Because he doesn't boil, there's no suggestion that the water is that hot. After Ackers falls in, and while Rogo tries to save him, there are two large explosions in the shaft; we can presume that, while Rogo was able to escape, Ackers was injured/trapped/otherwise incapacitated below the surface, and drowned.