The indestructibleness of the Prius never ceases to amaze me. The other day, I hear this clanging coming from the dryer. It's the Smart key. My daughter left it in her jeans, and it went through the entire wash cycle. It went through most of the drying cycle too, until it fell out of the pant pocket and started clanging around. I dreaded the thought of having to pay hundreds of dollars for a new Smart key. It turns out that the dryer saved the key, because it works just fine. I've heard of people dropping cell phones in the toilet, and saving it by taking it apart and blow drying it immediately thereafter. The dryer evidently did the same thing for the Smart key. I am amazed.
The SmartKey has UHF antenna. The antenna volatge is the highest inside the transponder. Water has high resistance compared with metal. When any electronics got wet, make sure you dry it complete first before you "try to see if it still works"! Once you activate the high-voltage antenna, no one knows what is gonna happen! The IC runs on <5.5V, which is safe with water. Drying it completely also prevents rust build-up. Don't give Toyota too much credit on this. Most hand-held electronics are like this. Dry it before you try to see if it still works!!! The moment you try it, it could fail!
Try it plugged into the dash. That part probably still works, as well as the mechanical key. As for the remote/proximity functions, take the sliding cover off, remove the battery, and just let it dry out that way for a while. Replace the battery before putting it back together. Might work.
Water by itself will probably not damage it if you let it dry out first. However, pool water also contains a lot of chlorine, so I'm not surprised that it died. As an aside, I recently spilled a full cup of water directly on top of my desktop computer, causing it shut off immediately! My computer sits on the floor next to my desk, and it has a large fan that blows air out the top, so most of the water went straight through to the inside. I was pretty freaked out at first, but since I also built this computer, I know a thing or two about them. Well anyway, I simply unplugged everything, dried out the insides as well as I could, and let it sit for about 24 hours to dry. The next day I plugged it back in, and everything worked fine!
