Wow! nice shot Scotchie..nicely composed.
Yes after some thought this is now clear to me... its a rocket returning from outer space and it has clearly just plummeted into the sea right here off Dover in spectacular style, completely gobsmacking the passengers on the humble catamaran. Its probably Soyuz 9 or similar. Why it didnt burn up on re-entry is open to speculation but the chances are it has been occupied by little green men, possibly from Mars, who have covered it with a protective shield.
They are now, as we write, swimming frantically for shore and are sure to amble up the beach anytime soon.
Expect to see them down the KFC later !