So you left your board floating unattended, and caused a windsurfer to have an acccident in which he broke a harness line (presumably a nasty catapault) and could have been injured and/or suffered expensive equipment damage.
What's your excuse again?
I had a collision with an unattended kiteboard a few weeks ago...like yours, it was bright red in colour, but believe me it was not all that visible - I'm always looking out for plastic bags, big jellyfish etc, but this thing had a fancy painted design which served to break up it's outline and was mostly submerged anyway; in the 0.03 seconds I had before hitting it I could've sworn it was a shopping bag, until I heard the loud crack of my fin against it.
There were no kiters in sight so I went ashore with the kiteboard balanced on the nose of my windsurf board...as soon as I stepped onto the sand, a guy came up and took it, said "thanks man" and disappeared. I hadn't even had a chance to check my board and fin for damage.
LUCKILY I did have time to examine the kiteboard - it had had a nice big chunk taken out of it! And it turned out that my equipment was undamaged!
"Thanks, man!"