Anyone who doesn't set the bar alt to match the radalt over the water and check it regularly is setting themselves up for a problem at night.
What use is the bar alt when you are making an approach to the deck of a vessel that could be 50 - 200' above the water?
I'm pretty sure the 135 has a baralt hold and possibly a rad alt hold in the AFCS so flying into the water shouldn't be possible in the cruise.
Did this one have 3 axis or 4 axis AP?