Two teenagers are in hospital after a scuba diving mishap in Victoria.

The 16-year-old boys were scuba diving at Portarlington when one spotted the other at the bottom of the ocean, an Ambulance Victoria spokesman said.

He attempted to rescue his friend and they may have come up to the surface too quickly, the spokesman said.

Both were airlifted to the Alfred Hospital with one in a serious but stable condition and the other in a stable condition.