World's Fastest Speedboat
The world's fastest speedboat was actually built in the backyard of the man who set the record. On October 8, 1978, at Blowering Dam, Australia, motorboat racer Ken Warby captained Spirit of Australia to a world-record average speed of 318.75 miles per hour, breaking his own record of 290.313 miles per hour set the previous year.
Warby designed and built Spirit of Australia himself, using balsa wood, fiberglass, and a military surplus engine he bought for only $69. This is a dangerous sport -- no other speedboat racer has clocked in at more than 300 miles per hour and survived.