It can happen. It happened to me. 3 year old girl, pond, long story short, nobody got hurt. This is a list of everything I had to do to the cart:
Cart was 2004 EZ-GO with brand new batteries. Stayed under water for about 30 minutes.
1. Controller was toast to the point that it could not ever be rebuilt. I sent to FSIP, they said it was too far gone for a rebuild.
2. Took floor mat up and blew water out of the ITS box. Got lucky on this part because any hairline crack in the ITS would have caused a replacement to have to happen.
3. Batteries actually survived, they were new. But like I said, it was only under water for 30 minutes.
4. Drained rear end oil and refilled.
5. This one I did not think of until later when I needed to work on brakes on the cart. The hubs had rusted to the axle splines. You should get your rear hubs off as soon as possible and clean and grease the axle splines.
6. Removed motor. Disassembled and cleaned and dryed and put back together. This should be done ASAP also because it will rust on the input shaft.
Cart has run great ever since. This happened about 3 years ago. Hope this helps and good luck.