Truth.
If you're not set on getting anywhere fast or pulling a tube with a half dozen people on it the best you can do new for <$25k is a small-ish bass or pontoon boat. With a pontoon boat you can fish, float, get some big magnets and metal detectors to look for treasure or maybe hang a hibachi off the side so we can learn your name in the papers later when they report the fire.
A jetski or two might be an option, trailering two of them is easy. With the right accessories they work for fishing, I've run across people snapper fishing on one as far as ~25 miles offshore on a smooth day.
FTLOG ... DO NOT get a fucking bicycle.
For a thousand or two (or three) you can pick up some SCUBA gear and use the rest to fund trips. Maybe double down and get both the SCUBA gear and the jetskis.