Puerto Vallarta crabs and snails

Hello everyone
Our family just returned from a few days on the pacific coast in puerto vallarta. Lovely place. My oldest went scuba diving out in Banderas Bay. He saw lots of great fish and invertes. Two days later when we were home in took two simular shells out of his gear. He picked them up because they were pretty. Long story short they were inhabited. I put them in a bowl of water from my nano and left tham over night. In the morning I had a snail in a three inch conch like shell with a red body and a crab with red legs and green claws. I did not want them to die so I put them in my tank that morning. I need a good picture to ID them. are they a safe addition to my tank? Any thoughts?

 

I wouldn't add them to my tank until I had a 100% positive i.d. on them and even then, I probably wouldn't.