The Everblades scored first on Matt Marquardt's first-period strike, but the second period was action-packed.
Elmira scored four straight goals in the first 10:52 of the period, only to see Florida string together three to tie the game at 4-4.
That score held up until 2.1 seconds remained in OT, when David Fischer found the net to give the Everblades the win.
Timo Pielmeier stopped 50 shots in the loss. Jordan Pietrus and Jean Bourbeau had one goal and two assists each, with Artem Demkov and Rob Bellamy adding the other two Elmira goals.
Game Four will be Wednesday night in Florida, set for a 7:30pm start.