Snorkeling question??? advice appreciated please...?

hi there, im going on holiday to egypt on monday with my husband and hes keen to go snorkeling. im a bit wary as although id love to try it and can swim a few lengths im not a particularly strong swimmer whereas my husband can swim like a fish for hours!!! is it possible to try snorkeling if you are just a basic swimmer? also, what do you actually do? all answers really appreciated