Comments about Cressi Cressi-Sub Fins Bag:
Holds my twin jet style fins, snorkel, mask in it's case, dive knife, gloves, booties weights, weight belt and my med. sized pneumatic speargun attaches to the loops on the outside with a fish stringer.
If you put weights in it, the shoulder straps on the backpack part of this bag need to be padded (those seatbelt shoulder pad things they sell in car parts stores are good).
The only thing you really need for snorkeling is a seperate bag to put your fish in, if you hunt.