Hey there, before Wilma there was some pretty nice snorkeling in front of the El Cid La Ceiba. The dive site is called "airplane flats", again, I don't know what's left, but there is/was remains of a small plane sunken in the '70's for a movie shoot just outside of the swim area. Inside the swim area, there are some nice small coral heads and usually a nice amount of sealife. parrot fish, cuddle fish, yellow stingrays, sgt. majors, triggers, butterflies & angelfish
You can access it by either going into the International Pier's shopping center and walking straight through to the beach where Seinor Frog's is at, or you could check at La Ceiba and see if they still have thier day pass, that will allow you access to the beach, pools, swim area and restaruant, food and drinks will be extra, but I think the passes are around $12 for the day/pp.
Another idea is Playa Corona, just up the street form Fiesta Americana, nice little day beach with good food, showers, bathrooms, plenty of umbrellaed tables for some shade. The snorkeling isn't great, mostly flat, grassy areas with some small coral heads. But like I said it is within walking distance of F.A., you could spend some time at both.
Of course this was all pre-Wilma, maybe Christi or someone else local will chime in with a current report on conditions at these places
the water proof case for keeping valuables in is a great idea. I have a waterproof bag that I use for both snokeling and diving to keep valuables in, works great snorkeling. with the added water pressure diving, it leaks occationally, but the dive master's don't seem to mind a soggy tip.
Have a great trip!