I had a wetbike in the 80's. They aren't fast, but can be fun to ride. It's a different riding experience, compared to any ski or couch. For $150 it's worth a try. Hauling them really sucks, since they're really narrow, tall, and top heavy. Finding parts is very difficult, too. If you get it running, you'll have some laughs. If you can't get it running, I'm sure you can part it out and make some profit off the other wetbike owners that desperately need parts.
BTW 2-up wheelies can be ridden for miles. That's worth $150 right there.