Impossible to flyfish in Cozumel without a boat, the reason is that the lagoon flats are not available by road.

You may tray Xcalac, that is even closer to Belize and I you can do it on your own, actually I just read an article in a maggasine about it, believe its call yucatan on your own.

I have never been there but I can put you in toach with people that have flyfish there. Very lonely place, no like Cozumel, very small hotels.

Pacho.