Thanks for the warm welcome guys!
Silkstone is very naughty to have raised false expectations of an interesting story around my screenname...
The truth is that several years ago I registered for MS Messenger or summat and the automatically-generated screenname was Gainful Shrimp. I decided I quite liked it for some reason, dunno why.
So the truth about my screenname is that it was a lucky accident.
Dunno about the sinking ship thing. I can't smell anything, Soupie, but then again my nose is now calibrated to deal with nappies.