Mumbles lifeboat and cliff rescue teams were called to the scene on Saturday afternoon.
Rescuers said the man had suffered multiple fractures and injuries following the accident at an area of cliff between Langland and Limeslade Bays, which is known for tombstoning.
Two RNLI lifeboat crews, Mumbles Coastguard Cliff Rescue Team, a Coastguard helicopter and Wales Air Ambulance attended the scene, and the casualty was airlifted to hospital in Cardiff.
In a social media post, Mumbles Coastguard Cliff Rescue Team said: “Tombstoning. Endless warnings. Yes he jumped from the top, no he didn’t know what was under the water and the tide was ebbing.
“He nearly paid the ultimate price but ended up with life changing injuries. Please don’t rock jump. This was near Langland Bay today.”
Lifeboat Deputy Coxswain James Bolter said: “We really are so grateful to the person with the cliff casualty who immediately called for help. This was a very serious incident. We hope all turns out well for the casualty.
“The Bank Holiday weekend combined with the easing of lockdown has meant a very busy Easter for the RNLI.
“We would advise anyone going near the water to ensure they check tides, weather and carry a means of calling for help. Remember if you do fall in the water the sea temperature is still incredibly cold”.
On Saturday, lifeboat crews were also called out to rescue a kayaker who had become separated from his kayak in Oxwich Bay.
The man, who was wearing a buoyancy aid, had been kayaking with a friend and his son in the bay when the tide turned. The other two kayakers made it back to shore, but one of the group found the tide too strong and was swept out to sea.The Kayaker found the tide too strong and was being swept out to sea.
He managed to make it onto rocks on Oxwich Point, which is where the Horton and Port Eynon Lifeboat crew rescued him