hey man i've surfed some with a drybag on my back before... the only
thing in the bag was a video camera and some fleece and a towel for
padding/wetness protection. now i was surfing some pretty decent
waves, not holes, in a hole i think it wouldnt matter quite as much but
on a wave it kinda throws off your balance and obviously wave riding
posture with your back arched kinda sucks with a backpack on. one thing
we would do is take turns with the back pack. one person goes down
without it and surfs, as soon as you see that person wipeout we'd throw
the bag in and then that person downstream would get it. it is for sure
logistically possible though.