While I'm usually the first to say "bad shaft seal" (SP 1600 Z 2 ), I like Al's approach.

If you can look closely enough, you can see if the water is coming from between the housing and the seal plate or from behind the mounting plate (they're close together and it's usually hard to get a good enough angle to tell the difference) - I'd do as Al suggests and try tightening the bolts before changing the seal assembly