I do pullups pushups and yoga, I went to the gym for years but feel better now surfing then when i worked out doing muscle building weight lifting kineda stuff. Everyones different but this works for me my muscles get tight easily. Running and mountain biking are also great cardio but I have to make sure i stretch a lot after or my hamstrings will be tight as a drum.
Get yourself P90X, an Iron Gym pull up bar, and an Indo board...this will help fill in the flat spells and keep you in shape for all your surfing needs...oh yea throw in some yoga as well. You are what you eat and do...don't take care of yourself and your body will fail you.