Deep sea diving

One day, a diver was enjoying the aquatic world 20 feet
below sea level. He noticed a guy at the same depth he was,
with no scuba gear on whatsoever.

The diver went below another 10 feet, but the guy joined
him a minute later. The diver went below 15 more feet, and
a minute later, the same guy joined him.

This confused the diver, so he took out a waterproof pad and
pencil, and wrote, "Amazing! How are you able to stay this
deep down without equipment?"

The guy took the pencil and pad, erased what the diver had
written, and wrote, "I'm drowning, you moron!"