Not so. The SEALs began in WW 2, IIRC.
(I was in Beirut with the last-ever deploying platoon from UDT-21, when it became ST-4. IOW, I was in Beirut with the first-ever deploying platoon from ST-4. The training, gear, platoon structure etc had been merged a few years before the shift.)
Me, then:
The UDT Teams began in WWII.
I had a friend over two decades who was a UDT warrior in WW 2. He claimed a bond with todays SEALs as a “plank owner”. A multi-talented individual who loved to fish, drink and relax. He also claimed offers to fly mysterious cargoes from Central America to the states. He was twin engine rated and passed on the “big bucks for no questions”.
No, UDT (Underwater Demolition Teams) were the WWII precursors of the SEALs. The SEALs were trained in all facets of special forces warfare, along with the underwater specialty.
That was the UDT teams. They didn’t specialize in direct action roles until JFK created the SEALs.
FWIW, I took my 78 year-old neighbor shooting this Saturday. He was with UDT 2 at Inchon. Loved shooting my CAR-15 and Glock.