Wow sorry to hear about the drone. Don't give up just yet. Can still be saved. Just rinse it with fresh water, or dab alcohol on it. But def upload the flight logs. If it was a malfunction then DJI should warranty a free repair/exchange. Failing that...
Dry it up, take it back to the shop and just say it stopped working. No need to tell them about the swimming in water part *cough cough* you have a 30 day exchange warranty and 12 months manufacture warranty.
If the shop tells you that it needs to be sent to DJI then be strong and explain that under the consumer rights act the sales receipt is a legally binding contract between you and the store you got it from. And unless it says on the receipt that the faulty product must be sent to DJI (which is won't) then they can't say anything at all. So legally they have to honor the replacement as it wasn't fit for purpose. Either way your covered for a replacement. [emoji6]