In the Round the island race on Saturday (1533 entrants) in the UK the yacht belonging to the commodore of the club that host the race (he was not on it) ran aground on a sunken wreck and sunk

This is a known obstruction and competitors often sail near it to shorten the course

Video of the sinking here iwradio.co.uk/2016/07/04/dramatic-footage-shows-alchemist-boat-sinking-at-round-the-island-race/

and a thread from a UK forum discussing it here forums.ybw.com/index.php?threads/the-ss-varvassi-claims-yet-another-victim.459808/

Interesting reading and watching

Regards Don