I think his GM is talking about the Ares Venture - 6 seats, Availability 12F, 400,000 nuyen... seems about right.
If he was actually doing watercraft, then it'd be hella cheaper: The Samuvani Otter seats 8, has BOD 12 and armor 6, and costs a pithy 21,000 nuyen. Hell, even the 2-person sub only costs 108K!