I'm no expert on sunk machines (a few guys on here are, to be sure) but looking at your pic, that's not a little bit of water getting into your subtrans, that's a full sink. I don't know how you can get to there without taking water into the motor.
Are you 100% sure there wasn't any water in the oil change you did? From what I've seen around here, guys do 3-4 oil changes to clean it out.
I'd also be going thru all the steps to assure there's no water in your fuel.
Sorry, not trying to scare you or bust your balls, I just dont want to see you get hosed.