I agree on the focal length front. 300 or 400mm reach is the starting point. I'd suggest 70-200 mkii + a teleconverter, or a 70-300L, 100-400, or a 300/400 prime, or a combination of any of these with a 7d/1d4. Depending on the spot, even 300mm is pretty short. I shoot surfing with a 300 2.8 IS + 1.4x on a 5d3 and am anxiously awaiting a new 7d2 so that i can get that extra reach back (and FPS).