Officially the bridges are supposed to be 65 ft with the exception of the Julia Tuttle in Miami. However
, more than one bridge might be a tad lower! In addition in certain stretches the water
might be a lot higher due to run-off or wind
blowing it in. If you're at the ICW height limit you have to really check the height before you try it. On most bridges there are boards showing the clearance. Also you have to make sure a big mother of a power boat
or even a small power boat
is not going to throw a wake as you go under. I have seen large catamarans back through bridges. I guess it's easier to go full ahead if you touch!