Hundreds of customers were enjoying a peaceful meal when they saw the vehicle float on the water before setting off across the sea at high speed.
Witnesses at The Hidden Hut in Portscatho, Cornwall, described it as like "being on a film set".
See also: Passenger ferry crashes into Canary Islands pier
See also: Booze cruise organiser 'Captain Calamity' rescued twice by RNLI
Management consultant Richard Robinson, 45, was enjoying a family holiday from London and was out for a meal with friends and family at the time.
He said: "Above ground it looks just like a Jeep, it's very cool looking and made a lot of noise.
1 / 15
The Mediterranean is one of the world's most beautiful locations for escaping on an adults-only holiday and offers the ultimate in rest, relaxation and grown-up fun in a child-free zone. Providing ridiculously dreamy views of the sparkling sea, impressive wellness spaces and incredible dining experiences, these adults-only hotels in Europe were made for couples, solo travellers and friends.
SEE ALSO: The ten best hotels in Spain
SEE ALSO: World-class dream hotels for your bucket list
Whether you're dreaming of Greek island bliss, Spanish siestas by the infinity pool or sunset aperitivi in Italy, you'll adore our pick of the best adult-only hotels in the Med. From Kefalonia's F Zeen Retreat to the Amalfi Coast's Monastero Santa Rosa, these exceptional hotels were made for grown-up breaks...