Welcome to Rootschat, Jerlow.
I haven't been able to find a baptism record for James Lowes in Rye but there is one possible candidate in Winchelsea (5km from Rye): James Lowes son of Martha Lowes, baptised 17 May 1801.
I've seen various Boulogne baptism records for children of James Lowes and Mary Ann Graves and he is described as a seaman, a steward on a packet, and a gentleman, but not a marine ( I think you must have meant to say "mariner"?).