Swimming
by Hayley
(Long Island, NY)
When I was away at college (landlocked in Michigan!) I swam 2-3 times a week. It definitely helped keep me in swimming and surfing shape.
I also took swimming lessons and dramatically improved my swimming ability. Obviously it was a plus not only in terms of fitness, but also for safety.
So, if you're unable to surf for whatever reason, I highly recommend finding a lap pool and adding a swim routine to your schedule.