When using commands(/spreadplayers) to disperse, players are dispersed to kelp and seaweed near the surface of the water.

Successful diffusion on the kelp(Spread 1 players around X,Z with an average distance of 0.00 block apart)

Can't diffuse on the sea without kelp(Could not spread 1 entities around X,Z (too many entities for space - try using spread of at most 0.00))