Marine organisms risk losing water to their surroundings because seawater has:

1. Water moves across a membrane toward the side with more dissolved solute. 2. Marine organisms are surrounded by water with a higher solute concentration than the organism. 3. Thus, they are in danger of losing water to the environment because of osmosis. 4. Freshwater organisms face the opposite problem and one adaptation there is the excretion of dilute urine. 5. The direction of the osmotic threat is set by which side is saltier. _Source: OpenStax Biology for AP(R) Courses (CC BY 4.0), Ch 35 'Ecology and the Biosphere', sections 35.1-35.5_