Sport Sub - By William Sleiniger and Jack Smith. If you're a skin diver of any experience you know that an electric powered sport submarine is great for underwater exploration. Seated in such a vehicle, you can cover more bottom simply because you do not expend your energy in swimming and your precious air can be made to last much longer. Also, Frances Gaar, the underwater swimming star who posed for our cover, will attest to the fact that it's great fun to operate.