The S-18 class sail is 1:178 (or near enough), compatible with the classic Revell Fleet Boat - but there never was a foundation S-boat kit for this. I'm bashing a hull from the (otherwise useless) Revell Nautilus "SSN" - a lot more work than most people would want to do - however if I'm feeling REALLY magnanimous, I will mold mine to make some (at least above-waterline) hull castings, to go with. Otherwise/until then, the builder would have to come up with a hull on his own.
Both the above are a "long story" here at ModelFleet - however most if not all of their (many) associated pictures went dark when I had to switch web-hosts, last summer. I do have all of them backed-up, so if there are any that you want to see, in particular, let me know and I will restore their links the soonest. (Otherwise, I will let the oldest posts just drop off, as my new storage space is limited.)