Dropped a valuable DSLR lens in the sea? You might think that you can pretty much wave it goodbye, but it is feasible to rescue salt water damaged lenses by boiling them.
When an $1,800 Nikkor 17-35mm f/2.8 lens was brought into a Nikon repair centre in Taiwan, the staff apparently rescued it with a little boiling. Not just in straight water — there's an unidentified chemical included in the process — and undoubtedly not a cheap process, but then for a costly lens, arguably worth it.
Nikon Repair Center Repairs a Salt Water-Damaged Lens by Boiling It [Petapixel]