The fish was originally completed in January 2007, the submarine a few months earlier. I had started on the fish first, almost 6 months prior, but I had gotten as far as the legs in back and then shelved it until winter. After I finished the submarine, I went back to work on the fish. Very little has changed since then - the tail on the submarine got an upgrade sometime in 2009, but that was it.
The fish and sub are both, roughly, minifig scale (in the approximate 1-foot to 1-stud ratio). After I had finished the sub, I then knew how big to make the fish to match.
I have placed this (fish only) on LEGO Cuusoo. Vote for this if you want LEGO to create a set like this!