G'Day Jags,
When you become a member of the WAKSA or AKSA, you are covered for public liability insurance for just such cases.

It isa strongly recommended that all kiters join WAKSA or AKSA. You are taking an unnecessary risk kiting on public beaches with no insurance.
Even if you collect a fellow kiter and injure them you need to be covered, check out the websites of both for the application form, it is only 60 bucks for a year and it gives you peace of mind.

On the reflective tape issue, silver and other reflective shiny stickers on your board attract sharks. There was a case in Florida where a guy riding a silver shiny board was actually bumped and knocked off his board whilst he was riding by a whaler shark.

The shark mistook it as the shiny scales of a tune or whatever and bit the board.

It is a nice considerate thought, but I would imagine running over a board on the river in a boat small enough to be damaged would be like finding the proverbial needle in a haystack. Best bet is to put your phone number on it next to the words, "reward if found", then at least you have a chance of getting it back if honest Joe finds it.
Just thoughts,
Darren Marshall
Australian Kiteboarding School