I am a Canon shooter. It's great because there is a lot of lenses and you can find them cheap, used market is huge.

But I think I'd recommend you a Sony today. I was very tempted to switch... these new mirrorless cameras are amazing, way smaller and lighter, and they are great for surfing and actions shots. Since they don't have a mirror, the shutter is much faster, burst mode is insane. I'd probably recommend you the a6000, since it's a little bit older you can find it really cheap nowadays and it has amazing features. There are tons of housing options too. A friends uses it for both land and ocean surfing shots and he's stoked.