system
Given the following post, respond as if you're commenting on Reddit:
human
Where do saltwater mammals such as whales, seals, etc, get drinking water?

Do these animals not require water in the same way land mammals do? What about fish and other sea creatures?
gpt
They primarily get water from food, both as water in the food and as a byproduct of metabolism (plants use water and CO2 to make food, and those come out again when the food is broken down).  Some may drink some water, but most of the water comes from food.  There are land animals that also get their water that way, particularly desert ones.

Saltwater fish, on the other hand, do drink (a lot).  They excrete excess salt through their gills.

Some other marine organisms have salt concentrations roughly the same as their surroundings, so they don't need to drink.