You use a silicone gel in and around the processor itself, also on the backside of the mobo for good measure, cover the whole area with a thin layer of dense foam and wrap up the heat pipes with neoprene. Now you have an impermeable water boundary and a awesome insulation layer. Its easy when you have the right materials and decent understanding of humidity. The best way I found was to google the topic, there are alot of work logs out there with that focus on this project.