The 19-year-old lifeguard jumped into the water to rescue Neil, who had already been warned about the strong currents. However the teenager became fatigued by the fast-flowing water.
As they were being swept away from the shore, a second lifeguard raised the alarm and a hovercraft sped to their aid.
They were both pulled to safety by the crew and taken back to the beach.
Mr Marshall said: "I dived in and swam out to him straight away but the current was so strong it was pulling me away and under the water, too. The boy was panicking and was distressed.
"My main aim was to keep his head above the water. I managed to keep us both afloat."
Last year Mark Caddick, of Walsall, and his eight-year-old son Matthew were rescued by the same hovercraft, Spirit of Lelaina, when they became stuck in mud flats at Brean Down.
The hovercraft is named after five-year-old Lelaina Hall, from Worcester, who drowned on June 23, 2002, after wandering a mile out to sea and becoming stuck in the mud. ..SUPL:
