I've been trying to recover a Phantom One after it was dipped "very quickly in fresh water. The owner told me everything was running perfectly so like a mug I bought it. By the time I got hold of it, 2 motors wouldn't spin and 2 ESCs needed replacing. Obviously there was no way it ran at all after being dunked.
Although the remainder of of the electronics was OK, every plug and socket were showing that greenish colour copper gets when it's tarnished. I've tried everything to clean it off, but a few days later it's back. The pins in the flight controller were very badly pitted, clearly the ex owner forgot to clean off and dry any of the connectors.
The worse hit was the GPS plug, the small white one. It's impossible to clean internally. As a last resort I doused it in Surgical alcohol and let it sit in a small container of it for a couple of days. I pulled it out and hit it with compressed air, plugged it in and gave it a dose of Conformal spray. At least no air will get at it again.
Everything's working apart from the two ESCs and motors, whether or not the GPS is working I won't bother with until I find replacements, which hopefully are on their way from Canada. It's currently lounging in the bottom of a cupboard with a container of Silica Gel, which doesn't appear to be absorbing anything, thankfully. It can stay there until those parts arrive. By the way, I tried to contact the ex owner, strangely he's refusing to talk. It's definitely the last time I use Bank Transfer and my dream of owning a DJI Phantom is just about over. OK, I know, it's only a P1, but when that's all you can afford it's good enough, or at least it was supposed to be. Good luck with yours Tom.