The question is badly written. Yes, it needs 2.5 m of water to maintain the flotation, yc will be the distance from the top of the platoon to the centroid of the weight, a trick question it maybe.
– r13Feb 18 '23 at 00:44
Check out [this question](https://engineering.stackexchange.com/questions/51717/ship-stability-and-overturning-moment).
– Tomáš LétalFeb 18 '23 at 07:06