These spawn underwater and wander to the shore in viking bay in Ragnarok, it's a recommended area, but their toxin put me under and killed me several times. Very annoying. My dinos wouldn't harvest them either. They're not made for land, but they sure don't care about that.
Be very careful about these-they do tons of torpor damage, I was down on the bottom of the ocean (on the island) and I saw a pack of these sea scorpions. I decided to dismount off of my mosa and kill them with my pick, as that would get more black pearls. When I got close to them one of them-a level ten hit me and knocked me out in one shot. I was level 88, wearing journeyman flak and apprentice riot. And they knocked me out in one hit. The moral of the story is that these things are very dangerous.