The nearest shore diving from Tampa is in Anna Marie Island, Sugar Barge or Spanish Rocks. They are both pretty meh, and over an hour away by car (like easily an hour to the exit and another 30 minutes to AMI). Beyond that you have Venice Shark Tooth diving, but that is probably 2 hours or more. And these times are from I75 in Tampa it can be much longer from downtown or from on base.
If you are here on a weekend you can also head up to one of the Florida Springs like Blue Grotto, Devil's Den, Rainbow River, or Ginnie. Or if you are willing to pay there are boat dives that leave from Clearwater like 2 Shea/Tanks a Lot or a couple of others.