There is a wasp they call the Jack Spaniel or Jack Spaniard: very nasty sting.
That looks scary, but wasn't it. Fatter and very black. It stung me through my swim trunks and did not leave a stinger.
On second thought I actually didn't get a good look at the one that stung me. I just felt that it was very large and assumed that it was one of the large black bees that often follow the boat.