These are the only signs that I could find - I think they appear in the IKO workbook. They don't seem super useful to me especially out in the water when dealing with a possible collision (as per aerial attack thread).
www.ikointl.com/intl_k_signs.php?menu_id=2I think learning your right of way rules are much more important especially in the surf. There's normally heaps of room in the surf. If someone is riding a wave or you notice they can't see you, change direction if safe to do so or get downwind of them if safe to do so.
2 Riders passing - upwind, kite high - downwind, kite low.
Look behind you before you turn. If following someone, expect that they could turn any second.
IKO right of way rules are here
http://www.ikointl.com/priority_rules.php?menu_id=2