Howard Park in Tarpon Springs is the closest. A little farther South is Caladesi State Park in Dunedin. Spectacular! It can only be reached by ferry and reservations must be made.
https://www.floridastateparks.org/park/Caladesi-Island
We take 75 to 50 west to 19 south to alt. 19. Gets you to both Howard Park and Dunedin. You miss the Tampa traffic.
There are no beachs worth going to North of Tarpon Springs in our opinion, until you get around the big bend.