I've lived in and around the Tampa Bay are for oer 30 years, and the answer is "yes" and "no". ALL small, inland bodies of water here in Florida do, will, or did contain some sort of gator life, and many incidents happen every year as a result of the ignorance of mainly unwary visitors--things such as the random golfer getting too close to the water's edge when retrieving a water ball...only to find a nest of 'balls' which turned out to have a protective mom nearby...
I just went kayaking up the Cotee River in New Port Richey yesterday, howeer, and never saw a single gator. They are there, and they are just as wary of you (us) as we should be of them--it's simply an awareness thing and that is all.
There are leash laws in Florida as well as most states, so yes--use a leash, do not leave your dog unattended outdoors at any time for any reason if you live near a body of water, which most people don't anyway, because of the heat.
I hope you find this helpful--for more thoughts and experieinces of Florida Living, check my blog: