I wouldn't collect the ones that you see on the land. If you go just a little way out in the water you should be able to see hermits. You should check to make sure that it is legal for you to collect marine critters in your area. Like misfit said, be SURE to QT.
Originally Posted by aloredo
I know this sounds juvinile
Not juvenile at all. Many aquarists collect their own aquarium inhabitants, instead of buying them from a LFS.