During COVID I spent a lot of time flying around the coast of Kenya, mostly following the coastline with a beautiful beach below me. And miles of horrible broken scrub inshore of the beach. So I thought about this a lot. I spent time visiting the beaches on foot to check the sand - tough job, but I’m prepared to make these sacrifices in the interests of aviation.
The conclusion I came to was that it depends! On a falling tide, a few meters above the water line, the sand was like concrete and would make beautiful landing site. Other places and times, the sand has a deceptively hard crust but under load it would break through into a void, I’m sure a landing on that would cause an instant and lethal flip. Dry soft sand well above the water would, I think, likely be survivable with a very nose-high technique, but would eventually cause a flip.
The beaches were generally deserted, so no worry about splattering sunbathers, but the shoreline also varied a lot depending on tide and location from rock/coral in the breakers to a clean gently sloping shoreline. It may be useful to have a rough idea of he state of the tide as part of your general SA.
So I conclude there’s no single answer to the question
sand or water, I was constantly updating my plan depending on what was below me, and I would probably have updated it half a dozen times more as I descended.
That was fun while it lasted.