Immersion-cooled condenser design

Hello again,

I am building a water-cooled refrigeration system which dumps its heat into the sea by means of a condenser immersed in seawater. In a worst case scenario there will be no forced convection in the seawater so I need to design the condenser to work with natural convection only.
The condenser will probably consist of a length of plain bronze tubing wound into a coil. The refrigerant is R134a and the heat load will be about 2.5kW, condensing at about 55 degrees C.
Does anyone know of any guidelines for designing a condenser of this type, or do I need to embark upon a horrendous tmathematical analysis? If this is the case, can anybody point me towards some appropriate heat transfer correlations?
My alternative plan is simply to build one and test it under various operating conditions. Has anybody already done this / is there any data available?

Thanks for any help,

James.