Which water based animals have a mechanism to prevent water from diffusing into their bodies

Osmoconformers are marine animals which, in contrast to osmoregulators, maintain the osmolarity of their body fluids such that it is always equal to the surrounding seawater. Osmoconformers decrease the net flux of water into or out of their bodies from diffusion.

Explanation:

i'm thinking (a) to keep sand in place; ////////////

explanation: a sand fence or sandbreak, like a snow fence, is used to force windblown, drifting sand to accumulate in a desired place. sand fences are employed to control erosion, sand dune stabilization, keep sand off roadways, and to recruit new material in desert areas.