Lived on the coast my entire life and can say that the ocean air is horrible on everything (including your house) save the fact it protects you against extreme temps! Ha
Technically every higher end camera has weather protection built into it so that doesn't matter. What does matter is the misty air when right next to the ocean. It plays havoc on your filters especially. You can take a look at my gallery, it's made up mostly of seascape photography. I've spent hundreds of hours at the ocean and haven't had a camera "ruined" by the ocean. I HAVE had plenty of gear ruined however. Remotes dropped into the water, tripod lubricant worn away and filters destroyed by salt. There's just no way of getting around it if you want ocean photos.
You can get the equipment or you don't have to. The equipment won't protect you over time, the salty air will still get stuck on everything when you take your camera out of the shell. I've never used that stuff, probably never will. If you're careful and not a spaz then you don't need it.
I forgot to mention, try not to change out your lens when right on the coast. You don't want that air inside your sensor. Again, goes back to being a spaz....... know what kind of shots you want before heading to the beach and you will only need 1 lens. I've had sand get inside... not good.
I live on the cost and it can be a problem for anything ,,, salt water really does do a lot of damage to anything mechanical or electronic.
In saying that I dont have any problems with it , dont let any sea spray get on your camera at all and you will be fine .
For shooting on the beach or close to the water I have a few UV or skylight filters that I have glued plastic bags to and I simply screw on the filter and cover the camera with the bag, this way I can still shoot on the beach with all the sea spray but none of it gets to my camera or lens at any time. Any film or lens changing is done in my car or not at all , I would NEVER change over a lens while on the beach .
If you are unlucky enough to drop your camera in the salt water then it a 99% chance of an instant ruin , I have dropped a 6x6 medium format myself and while I manged to repair and clean the body the lens was a total right off.
I know it causes a lot of damage to metals and speeds the process of rusting. Usually why vehicles down near the coast have a coating of some sealant on the paint and the metal. I won't be there for a long time. It maybe a possibility of taking it down near the beach but I don't know if I want to risk it.
If it is turned on, it's ruined. If it isn't, there is a good chance you can save it. The temptation to turn it on and see if it is still working will be almost overwhelming and you are going to have to resist that. If you do turn it on, that will kill your camera. IMMEDIATELY take the battery out and dunk it in a bucket of distilled water. Let it soak until bubbles stop coming out. Pull it out, drain it, and dunk it again. Pull it out the second time, open it up, and let it sit there for a month or so until all traces of water have evaporated. When you are absolutely certain it is completely dry, inside and out, put the battery back in. Odds are pretty good that it will start working again. The trick is to get rid of all the salt.
I live right on the ocean, and only owned weather sealed camera bodies (Canon 10D and 5D mk2). The second camera exhibits slight rust around exposed hotshot, but otherwise it's perfect. After nearly 10 years both cameras perform fine.
It can, over a long period. Salt is corrosive to most metals, especially steel and iron, but also to brass, aluminum and copper (to a lesser extent). That said, unless you leave it outside overnight, or get it drenched, you probably won't get enough inside the camera to matter over the course of two or three weeks. Just wipe the body down every now and then with a damp rag and clean the lens when you see specks of salt on it. Far more dangerous to photographic gear is wind blown sand (that stuff all over the beaches). I would not take it out on a beach on a windy day if I were you, but other than that, you should be all right.
And the answer is yes, the sea spray can increase the corrosion on electronics. It's not so much the moisture as the salt as well. Over the course of a trip, I'm not sure it's enough to worry about, but it is something which does happen.
To play it safe, you could get one of those water-proof pouches that's usable under water. But, realize that you're mostly protecting it against rain as I don't think sea spray exposure over the short term is going to represent a huge risk.