6ebbba77_Marine_habitats__principles__Living_in_the_sea
[Factor] Body shape [Living on the land] Most animals (except birds) are not streamlined. Wind resistance does not affect their speed very much. [Living in the sea] 
Since water is 800 times denser than air, water resistance affects speed very much. Fast fish are streamlined. Fins propel efficiently, legs don't.
Marine habitats, principles
Living in the sea