There was a PBS show on the same sub & dive(s). IIRC there were 2 deaths, father & son, on one of the dives. They did eventually ID the sub which had been thought to have been lost in another area. As far as deep dives go there was another show I saw recently where the divers were recovering gold from a WWII transport ship. They were working saturation dives in what I thought was deeper than an unprotected (not in a hardsuit) diver could go. I think they said 600' ?!??!??
Perhaps the divers here could comment on either/both ...