The most common cause of pee that smells like fish is a UTI or Urinary Tract Infection.
The Urinary Tract Infection is a bacterial infection that occurs in women's vaginas that lead to a fishy smell from the urine.
Although UTI or Urinary Tract Infections are mostly common in women it can sometimes affect men as well if the bacteria gets into the Urinary Tract.
If your pee continues to smell like fish you need to see a doctor and get your urine tested and have the Urinary Tract Infection treated.
Kidney Stones can also sometimes cause fishy smelling or foul smelling urine but you would usually have other symptoms such as sharp pain on the side of your body.