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Clamsmasha said..
Water "sticking" to wing or fin can be useful, better it stays attached to the top of the wing than separating early. It's a different application to pushing your gondola across the lineup or an America's cup yacht etc.
I do not know what you are trying to say, but sanding a glossy finish makes the water stick to the board/foil surface. This is why it reduces drag, as the drag water on water is lower than water on hull. It also make the separation happen very late.
And the effect is noticeable when entering planing, I experimented it on SUPs and sailboards. Not so much for paddling around.
A surfboard travels between 10 and 20 knts on a wave. Even at 10knts the surface friction is 5 times lower for a sanded finish than a glossy one. Of course it is only a fraction of the total drag (which is composed of friction, form, lift-induced - for the foil -, wave resitance), but you get the idea... and foils travel even faster.