The urinary system of a shark includes a bladder and urinary tract but unlike bony species of fish, sharks do not expel that urine through the traditional urinary system.
Sharks need to maintain a steady level of soluble salts in their body at all times to maintain buoyancy and avoid dehydration from seawater running over their gills.
To achieve this, they will convert their urine into urea that they can store in their bloodstream. Excess urea is absorbed into the muscle tissue and expelled through the animal’s skin.