Ancestry has recently included Mates and Masters tickets for UK and Ireland from 1850-1960(not sure of end date!) - just put the name in. Generally crew did not have families with them, but if the Captain did not I suppose he might have allowed the 1st (or only) Mate to do so - or is it possible your William owned a share in a boat which might have given him some privilege? Also, what exactly is meant by "exotic things"? Have any of them survived or is it a myth like "state rooms". Of course he could have done more than coasting but proof is needed. As before, as he came from Shields I would suggest you try Tyne and Wear - if they do not know they could probably point you in the right direction. It could also be worth googling "Deaths at sea" - if recorded there is a register.