I used to own a place about four miles south of the center of Tarpon Springs and did a fair amount of local diving there. It's true that the ocean diving options are more limited, and, due to the dive sites being farther offshore, more expensive than on Florida's east coast. But the area is not a total diving wasteland. If you'll have a car, I'd strongly suggest checking out some of the freshwater springs a bit to the north. While northern Florida is one of the world's big cave diving areas, there are plenty of dives suitable for open water divers, including new divers, and it's a fascinating kind of diving you don't find just anywhere. Do some Googling on "Florida spring diving" and you'll see what I mean. Some specific sites to consider might be Rainbow River, Manatee Springs State Park, Devil's Den, Blue Grotto, and, a bit more of a drive but fascinating to dive, Ginnie Springs. Think about snorkeling with the manatees in Crystal River, if Three Sisters Spring, is open. Pick up a copy of Ned Deloach's Diving Guide to Underwater Florida - it's quite exhaustive on all these places and more. Mac's Scuba and Narcosis are two dive shops right in Tarpon Springs that I can recommend to help you plan this, as well as offshore charters.