You don't realize how dense that old growth pine is. There's a stretch between Pembroke and Ottawa it was all logging. Our nation's capital was built with it. They brought the logs up the river to Ottawa many sank to the bottom. Fast forward to now I have a freind who harvests those logs brings them to the surface and inside there perfectly fine that's after 150 years under water.
I've heard about those sunken trees before. Pretty cool.
This stuff is super hard. You can hardly drive a nail without a nail gun and unless you pre-drill or use high quality deck screws, it will wring the head off of a screw in a heartbeat.
A benefit to that hardness is that termites give up on it. Unless a water leak weakens heart pine, you won't find any termites with strong enough teeth.