Thought this was interesting. Shows some pics on making one of the thunderball mini-subs. The manta ray was a cowling over an Italian made (Cos.Mo.S) Seahorse-II two-man SDV:
http://www.hisutton.com/Thunderball%20- ... movie.html
Seahorse 1 wetsub:
http://www.hisutton.com/The%20famous%20 ... iot.htmlou
You can poke around to other pages like the history of Seal delivery wet-subs:
http://www.hisutton.com/US-Navy-SEAL-De ... Mod-0.html