HCA: Hermit Crab Association

I was searching up about hermit crabs and i seen that it says they need freshwater and saltwater and land to survive but I've also seen some people just put a species of hermit crabs called left handed hermit crabs in saltwater alone are these fine with saltwater alone?

I think you are talking about marine hermit crabs? This site is basically only about land hermit crabs, so you will have to probably research elsewhere. If you are talking about land hermit crabs, then they do need all these plus more. I think the land/ freshwater thing is only for land hermits. I don't know anything whatsoever about marine crabs though.