When ashore they drink salt water from anywhere they can find it, plus even off themselves if it rains. But this only happens when they’re ashore for breeding.
When at sea they have no choice but to drink saltwater either directly or through the fish they eat. They then do as honeybee and smartie said, and get rid of the excess salt that’s contained in their blood by using special glands as mentioned. It’s then expelled through the nostrils/beak.
.....smart
