Other lessons to learn if your electronics has taken a swim: wash it right away in distilled water (or at least fresh water from the tap), and don't try turning it on until absolutely positively dry. Otherwise, if you did try to dry it and turn it on without rinsing it, you might get one or two random boots with the camera's flash LED blasting on and off erratically followed by nothing at all. Completely and unretrievably dead. Yes, despite knowing better, I made that mistake too.
However, even if you do everything wrong like I did, you'll be happy to know that there's still a chance you can get your device back to life. I had nothing to lose from completely disassembling it, giving it a good clean, and putting back together. Either that, or spring for a new phone. So once we were back from our Costa Rica vacation, here's what I did.
1) Acquire a very tiny Torq screwdriver - T4. In Ottawa, very few places carry it, but one that does and is super helpful besides is Canada Computers and Electronics. They have the iCAN32 toolkit, a handy little driver kit that has the needed T4 and a ton of other cool electronics bits for a mere $9. Peanuts compared to a new phone.
(Lee Valley is the first place I thought to go, but they won't have what you need. Their electronics screwdriver kit doesn't have the T4 or smaller bits. And Ottawa Fastener Supply is super cool, but they won't have a T4 either.)
2) Disassemble the Z10 according to these youtube videos:
I referenced both, but I preferred the first. I didn't pull the screen (it wasn't necessary)--just popped off the case and extracted the motherboard.
3) Scrub out all visible corrosion with rubbing alcohol and a Q-Tip. Even though it was just in the sea for a minute or two, there was quite a bit of surface rust, salt, and copper oxide. Most of it was around the battery contacts and camera, but it was on some of the shielded chips too. I was able to get most of it off, but not all.
4) Bathe it in distilled water. I gave it about a 10 minute soak and gently agitated it (swished it back and forth) in a small bowl of distilled water to try to get any salt that may have been underneath the shielded chips to dissolve.
5) Gently shake it off, then pack it in a bowl of white rice overnight to extract any excess water.
6) Reassemble it and plug in the battery.
I had my fingers crossed and held my breath for the seemingly long time before the screen lit up, but... IT WORKED! I ran the BlackBerry Virtual Expert and I only had one casualty--the camera. While the "selfie" camera worked, the main front-facing camera was completely dead. It was probably giving itself a nice shorting out while it going berserk flashing on and off after I turned it on. Whoops. (Anybody have an otherwise dead or defunct Z10 that I can salvage the camera from?)
Everything else worked perfectly! Especially rewarding as I never backed it up, so would have lost everything on the internal flash.
The moral of the story is even if you soak your phone in a conductive sea-water bath, and try to turn it on and it's dead, you may still be okay with a little work and a lot of luck. Don't lose heart!