Waves can dislodge mussels and draw them out to sea. Gulls pick up and drop sea urchins to break them open. Starfish prey on mussels and are eaten by gulls themselves. Even black bears sometimes feast on intertidal creatures at low tide. Although tide pool organisms must avoid getting washed away into the ocean, drying up in the sun, or getting eaten, they depend on the tide pool's constant changes for food.