Well, just my opinion, it seems to me it's all an optical illusion as far as "apparent" size goes. True size of sun or moon of course don't change, and despite what people may think the atmosphere does not "magnify" either sun or moon when it's close to horizon.
What does happen with respect to the sun at sunset or sunrise, is all that intense light is being scattered thru a much thicker layer of atmosphere than when it's right overhead. And the light is more diffused. So the light "spreads out" more, if that makes sense, and it is possible to actually observe the sun's disc for a second or 2. Try looking directly at the sun at noon on a clear day, well you can't do it so you have no point for comparison!
The moon otoh, is like a candle in comparison to the sun's searchlight. You can look straight at it, as long as you like, no matter where it is. And there is very little light to get wildly scattered by that thicker layer of atmosphere when it rises or sets.
So anyway, the moon's size is more familiar. On land, when it rises or sets you have all kinds of familiar references to compare it to - buildings, trees, hills and so on. When it gets overhead your reference points are taken away and as a result it appears smaller.
But at sea, you don't have any of those reference points. Nothing but a flat, featureless horizon which is little better than the zenith of the sky. I've never been at sea on a clear night with a full moon rising, but I'd bet it wouldn't look much (if any) larger when rising than when it was right overhead...
DH
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