I seem to remember reading about this theory back in the 90s. Large deposits of methane gas beneath the Bermuda Triangle release and knock ships or even planes on their keister, sending them to Davie Jones's Locker. An article posted last week over at LiveSciene talks more in depth about the theory, never bothering to use the word "keister" in the whole article...that knocked me on my bum!
But the short of it is methane deposits explode, sending huge balls of gas top side, they hit a ship, knock it over, it sinks and vanishes so fast they don't have time to alert anyone.
What it doesn't explain are the half eaten corpses found on abandoned sailing vessels and merchant ships that come back from the dead!