I rarely post on forums, but since this is right up my alley, i'd drop my 2 cents:
- gym work doesn't transfers to major improvements in surfing, but could be useful for conditioning and perhaps more power. however, you want to get better at surfing: surf more. use different boards: Logs, twin-fins, eggs, thrusters, quads, one mans. go body surf, dive, paddle, swim to maintain some endurance. stay out of the pool if you can.
- hypertrophy work and surfing don't mix. stretching and surfing do. i found hill sprints and the C2 would work wonders as well. after playing with my prowlers, i could see that working.
- the more i get into training the more i think Kelly had it right back in 2002ish. his routine consisted of lots of leg work and a boat load of stretching. i realize the fascination behind Mick, especially from an aussie, but the freak has 9 world titles. not sure if he squated, but i could see some 3-5 reps and under working, w/o packing on too much meat. lots of bang for the buck there
- this might be getting a little geeky, but look at the type of surf you typically tackle. beach breaks require more sprint work. point breaks need more endurance stuff. tow-ins need more work underwater/mental work...etc.
- unless its firing, limit marathon sessions. one hour tops, refuel, rest/nap, repeat. catch as much waves as you can in that hour. if you can find the time do that 2-4x / day
- xfit....i ran with that for a while, and it worked wonders for several months. then my shoulders started to hurt from those damn pull-ups. read lots of stuff from gant, DJ, JW, etc. and started questioning xfit. left it a year ago, got into smarter programming, stopped doing stupid shit and what do you know, i got stronger and was in less pain. i see the benefit in the metcons, though i rarely do them now, but if you keep them to BW stuff (w/o kipping in any form), maybe some KBs, Litvis, sprints, it could work. don't get hurt and take care of your shoulders
- squat! look at any surfer and 99% have chicken and/or weak legs.....major imbalance there. the exceptions are carroll, kelly, sunny, poncho. make your legs strong, your turns will throw more chunks. (C&J's and Snatches would definitely work, if you can find a proper coach....but that could get you addicted to olys.) we all can't be as smooth as parko or a quick as mick...
to sum: my advice would be to squat, sprint, stretch and surf....lots and lots of surfing