I chartered out of St. Petersburg several times in the early 1990’s, but most recently in 2002, plus lived there between 1987 & 1999 while owning three boats, two sail and one power. The company I used in 2002 was in the location where Tampa Bay Yacht Charters now is in Bayboro Harbor. Charterers out of St Petersburg would likely head SE to lower Tampa Bay and down the ICW or along the Gulf Coast to Sarasota Bay. But if you charter from Tampa it’s about 20 n.mi. to the Sunshine Skyway Bridge just to enter lower Tampa Bay. If departing St. Petersburg, it’s only ten. It’s about 15 n.mi. from St. Pete to De Soto Point on the Manatee River. A very nice anchorage, plus there is a National Park ashore. This is the suspected spot of Hernando de Soto’s FL landing in 1539. That spot, De Soto Point, is NOT the same as Fort De Soto.
If wishing to continue down the ICW, the “entrance” known to locals as The Bulkhead is maybe two n.mi. beyond the mouth of the Manatee River. Whereas day shapes mark the channel, one needs to also use the range marker to align on nearing the first turn. If you’re out of the channel, you’re aground.
Then there are two drawbridges to pass under heading down to Sarasota Bay. Moore’s anchorage, a nice spot, is a short distance past the second bridge. But the nicest little secluded anchorage is at Otter Key, beyond the Ringling Causeway Bridge and off Big Sarasota Pass (but don’t go out the pass; you’ll overshoot it). That’s about 40 n.mi. from St. Pete and a good turn-around point if a 4-day (3-night) charter. If you get a 6-night charter, or longer, and wish to push each day you might make the 100 n.mi. (one-way) trek to Pine Island Sound. Anchor in front of Useppa Island. But if going that far you might wish to travel outside if favorable weather, past Anna Maria Island then SE along the coast. Enter the Sound at Boca Grande. Our turn-around point in 2002 for the 6-night charter was Venice, about 60 n.mi. distant. For more detailed suggestions, you’d need to identify a destination area or objective, etc.
If you wish to just hang inside Tampa Bay, anchor in Brightwaters (St. Petersburg) for a couple of nights. A shallow passage going in; potential problem if > 5 ft draft, but very pretty and protected. There’s a spoil “island” over near Apollo Beach on the eastern shore and lying more within the Tampa end of the Bay. Popular spot, and easy. The spoil is high enough to go ashore and walk around. There’s more depending on where you wish to be, etc.