Thanks folks. I went out late last night, and it happened to be night time in the game (not sure if that matters) and there was 1 on the beach, so I killed him. That left 2. I did what some of you said and killed a few more of the critters around, and that might have helped, as one more showed up, and then another a short time later.

Was a bit concerned because there were so many that first time I went down there, but nothing the 2nd time, and only one at a time when I finally finished.

I never did try the NW trick, but thank you the same

@Archadius - and now, I have successfully eradicated them!