system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How do birds that dive from the air into the water to catch fish manage to get back up into the air? Wouldn't the water soaking their feathers weigh them down?
gpt
Birds have an organ called the Uropygial gland, which is an excretory gland that produces oil for their feathers. Birds will use their beaks to spread this oil over their feathers.

One benefit of this oil is that it makes the feathers waterproof.