wrote
40 foot sailboats sail very close to each other all the time when
racing, so it doesn't seem that unusual.

Maybe, but I consider myself pretty darn close when I'm less than a boat
length from somebody. The difference in a racing situation is you expect
other boats to be there and you have a pretty good idea where they're
planning to go, to say nothing of the fact that you'll seldom run into one
ten times your size.