Children belonging to the Moken tribe of Thailand have perfect vision underwater. They do is by constricting their pupils and changing their lens shape, just like dolphins and seals. They use this ability to hunt for fish, clam and shells to eat. This skill can be acquired, when exposed to underwater environment enough at an early age – before ~5 years.
The US Navy diving manual has detailed instructions for escaping a giant clam.
James Cameron made the movie Titanic to get a dive to the shipwreck funded by the movie studio; not because he particularly wanted to make the movie.
Two scuba divers were left behind while diving in the middle of the ocean, they’ve never been found.