It looks somewhat rediculous, but this little fella's the result of over a month's work, trying to come up with a simple, easily constructed, completely water tight and low resistance sealed couple for the system.
It actually works very well. Not sure how it would hold up in a higher torque/rev situation, but for this application it's perfect.

The rest of the setup is the basic frame and gearing for the device: Worm drive - down gear - universal. The last being just a section of washing machine hose, which being light, easily sourced and only flexible along it's length (while very resistant to twisting) is again, perfect.