From "Without a Trace" by Charles Berlitz, 1977. I spoke to Marvin McCamis in 1997, who told me Berlitz had the date wrong and it actually happened in July 1965.
Jay Michael Cooney [of Bizarre Zoology] asked: What was the whole story?
Dale Drinnon replied: This was seen by the exploratory sub "Alvin" on a trip down into the "Tongue of the Oean". a very deep part of the sea around Gran Bahama island, something more than a mile down. The man in the sub said he saw a creature that looked like a plesiosaur. A fellow sent me a letter a while back saying he had seen the bona fide carcass of a Plesiosaur in Scotland in 1942, and he said it looked like this one. A couple of features he mentioned made me think it could have been legitimate. Thanks for putting up a copy of this, I've been trying to get one for ages!
[The carcass in question was supposed to have been washed up by a storm near Prestwick Airport, then under construction as it was during WWII. the man said the whole head was intact, he looked into the mouth and saw teeth. This is one ofthe features which sounds legitimate. The body was eventually buried in the sand on the beach, presumably, and when seen it was about half-buried. It was not an especially large one, it was about twenty feet long. The witness was William Whammond, an ex patent attorney and writer for PURSUIT, then resident of Quebec.
On the blog which carried my xerox of the illustration of the Plesiosaur seen from a cliff in Wales also mentioned this sighting as an example of a Long Necked Sea Serpent seen to have a tail when the whole creature was clearly seen, in direct contradiction to Heuvelmans, and I assume that Scott Mardis was only following up on my statement when he scanned this.-DD]
ADDENDUM: Scott Mardis has sent scans of the relevant passage of Without a Trace by Charles Berlitz along with other relevant materials including biography of the witness in the case