......................Is it likely John Hood could easily change occupations ( Mariner to Waterman) ?..........
Hi, I can't see a problem with a Mariner later becoming a Waterman 
Frank.
Especially if his mother's new husband is a waterman

I cant find a baptism until a few years after the marriage of George Hood to Eleanor Wetherstone, but that doesn't mean there wasn't one - we don't know the condition of the PRs.
I'm liking the possibility of George Hood son of John Hood son of George Hood.
There seems to have been quite a few Hoods marrying & having children in Newcastle around the same time - Leonard, William, John & George Hood at first glance.