Rex Research is a great site, chock-full of info about wacky inventions that never made it, including a bunch of free-energy quackery and pseudoscience that’s still a lot of fun if you take it with a grain of salt. One of my favorite pages so far is this collection of weird-ass boats that folks have made. Highlights include a boat with tank-like treads, a submarine that swims like a fish, and an active-wave-cancellation system for aircraft carriers.