Does all boats have foam in the floor?

I have a 1984 Cheetah 142 bass boat and was wondering if there is foam on the floor that can get water logged? The floor is awful close to the hull of the boat being it's s tri hull. I ask because I installed a depth finder a couple of days ago and when I drilled into the transom water trickled out. Could this be coming from the transom or is it water logged? I can move the boat around on the trailer by hand with no problems really so it's not real heavy but I'm concerned about the water in the boat. I do know the transom needs work but the floor is solid to me. What do y'all think? It's a 14' bass boat with s 25hp Mercury on it.

Ayuh,... The odds are, Yes, there's foam in that hull somewhere, probably under the deck,...

Did you drill through the transom all the way? It may have a doublebottom without foam but it should be dry. Does the boat sit outside in the off season exposed to the elements? It may be worth it to hire a mechanic to do a complete survey of the hull if the foam is water soaked it needs replaced. It is labor intensive and if the transom has dryrot you need to determine if it is cost effective to repair or replace. Find the specs for the boat, motor and trailer and then have it weighted. Back then they used the cheap foam that absorbs water and the only way to remove the deck and chip it out.