You did right to rinse the camera out, but you want to make sure you really, really get all the salt out, even if it means soaking the camera in fresh water for a while and swishing it around. The salt water was under pressure, so it probably got into all the little nooks and crannies, and just rinsing it under a tap will not get enough of the salt out.
One challenge is that because the camera is sealed around all the other openings, it will be hard to dry it out, even under a fan, in rice, or using some other dessicant.
Another major challenge is that you won't be able to clean the inside of the lens, if it has any residue. Even if you get all the salt out, there might be some lubricants that were displaced and settled on the lens.
Note that the WG-1 is an older model, and better models from are available now, from Ricoh/Pentax a well as the other manufacturers. For example, the Ricoh WG-20 is readily available to you in the US (if I read your profile correctly) at Target retail stores, for under $200, and it looks like it is currently on sale for $159.99. The WG-20 is intended to be a lower-cost model than the current top-spec Ricoh model, the Ricoh WG-4; but from what I understand, the WG-4 it is based on the Pentax WG-2, so it should still be more capable than your first-generation WG-1.
Of course, since your buddy should be buying, you could always go for the WG-4. which does run about $300, similar to (or even a little less than) what the original WG-1 went for