It might be the thru-hull for the depth sounder transducer. See what the surveyor has to say about it, but if there is to transducer to go in the spot, it is not a big deal to glass up and fill the hole. Leaving just a wooden bung in the hole is not a good idea.
Thanks guys for the replies! I will wait for the survey, but it looks like the hole was part of manufacturing not after. I pulled everything out of the Vberth area and looked below. There is a water holding tank, but I think the hole is still towards the stern from there?
Besides glassing over it, what could be used as a permanent plug?