With snowboarding, you are sliding downhill and it's guaranteed you'll get some speed (either through riding or tumbling). But you'll get down.
With surfing, that is not guaranteed. As a starting surfer, I have often been in the water for 2 hours and not caught a single wave. But when I know I'm about to catch a wave, there's a certain rush that happens. For me, the thing that keeps me coming back is not even riding the wave (probably because I haven't ridden many and don't know how good it can get yet). But the thing that keeps me coming back is the gush of dopamine I feel RIGHT before I get up on the wave. When I feel my board catch, and all my brain keeps firing off the question "IS THIS ONE MINE? THIS ONE IS MINE!!". The build-up and climax and rush of bliss felt at that moment is only comparable to.... an orgasm? (I wouldn't know cuz I've never experienced one. Lol jk.) But some moments that I've felt that, I didn't even catch it, because the split second after, I lost balance or misstepped and crashed and burned into the cold surface of the wave and was trashed and tumbled.
Ok, maybe it's similar to jumps in snowboarding. With jumps and tricks, snowboarding becomes a different beast. Because there is build-up. There is the approach to the jump and all the sound of the board sliding against the snow as you make minor adjustments and try not to shit your snowpants. There is the ramp up, which goes by in a flash, as you kind of stop thinking. There is the jump, and you become airborne and all the noise quiets down as if you've just entered the vacuum of space. And it has been bulding-up... to right about now. To right when you land, and you KNOW that you'll stick this one. And you stick it. Or you don't, and you fall hard, and really do shit your pants. (I have come close - to where it took all my strength to hold my sphincter.)