DSLR in sand and salt water

It's toast.

Salt water is the most corrosive thing you can do to the electronics inside a DSLR that doesn't involve a vat of strong acid.

Roger Cicala, the founder of lensrentals.com, has posted at least two blog entries regarding teardowns he did of rental cameras returned after having been exposed to salt water without having actually been submerged in it.

The Fujifilm GFX 100 vs Salt Water Teardown
About Getting Your Camera Wet… Teardown of a Salty Sony A7sII

According to Roger¹, saltwater damage is more devastating to cameras and their internals than just about anything the gear his company rents encounters on a regular basis. He covers it in depth in this blog entry, but he has also mentioned it in many others.

The results were not pretty.

This is a portion of the main PC board of a $10K Fuji Medium Format GFX100:

Here's another part of the same camera:

This is part of a Sony α7S II:

At Roger's company, they don't even part out unrepairable cameras with salt water damage due to the concern that there may hidden corrosion in those parts. Normally, those guys part out just about everything - even some full frame cameras with a single scratch on the sensor get parted out to repair other cameras in their vast inventory:

Lensrentals insider joke: What do you call a D800 with a scratched sensor?
Parts.
Because at $1,800 for a sensor replacement . . .

But in the case of salt water damage:

But the amount of salt and corrosion here and on the bottom means we wouldn’t trust anything in this camera, ever again. It can’t even be a parts donor — the chance that those parts will eventually corrode and fail is too high. That’s why many service centers won’t repair water damaged cameras; they have to give a warranty after the repair and chances are very high something they didn’t replace is going to fail during the warranty period.

_{¹ Probably no one in the world oversees a larger inventory of cameras and lenses that are used to take photos, rather than being stored in a warehouse as inventory to be sold, than they do.}