My D-800 may be dead

Once your friend or anyone else gets into the canoe, you no longer have control or can predict what will happen.  To take it a bit further, even if you got into the canoe by yourself, there was still a possibility the camera could get wet and, at worst, could have been submerged in water or lost in the water.  That's just the risk that you have to take.  When another person got into that canoe, your risk increased many folds.

Your friend should have offered to help compensate, but $3k is alot of money and I'm not surprise he did not offer.  If it was me and I did cause this, I would balk at full compensation.  I would compensate 1/3 or 1/4 and be extremely sorry.

Gary