Hey Margie,
I do not have any experiences with the Ewa-Marine housing personally.
If you use the housing/bag only for snorkeling in safe environments I think
it do its job for a reasonable price.
What kind of photography do you plan with the ewa marine housing?
Do you just want to photograph in wet environements? Do you want to
shot underwater scenes? Does the shooting happen under rough conditions
(rough waves, starting the shot from a boat, .. )?
The ewa marine is good if you are snorkeling on a beach, want to make some
halt and half shots or you just want to have some water protection.
ciao Lars