Figure 36.6: Osmotic Regulation and Conformity When ocean invertebrates enter waters where the salinities are lower than in the ocean, some (such as mussels) are osmotic conformers and allow their blood osmotic pressure to match the environmental osmotic pressure. Others (such as many crabs) are osmotic regulators. They keep the osmotic pressure of their blood from falling as low as the osmotic pressure in the environmental water, and their internal osmotic pressure is therefore more stable than the environmental osmotic pressure. The osmotic pressure of seawater is 1,000 mOsm.