So due to user error, I accidentally landed my Mavic Pro in my backyard swimming pool. It sunk to the bottom and I recovered it within 30-45 seconds.I immediately placed it in a bag of rice and let it sit for over 3 days.

The battery didn't work anymore, but I took a brand new battery and the drone powers on. However, it won't actually take flight. The motors spin the propellors, but it sounds as though it doesn't have enough "ummph" to actually take off. Video of it in action https://www.icloud.com/photos/#0SqddYjVvXT2GaT527ZSCxNmw

I updated to the latest firmware and everything, but I can't get it to fly.
Any suggestions on parts I could attempt to replace? Maybe buy new motors? I'd hate to have to buy a brand new drone if I only need to swap out a few parts.

Hello there laphlaw. I am sorry to read and to know what happened to your DJI Mavic Pro and thank you for reaching out. Since this unfortunate event happened to the said DJI Drone I would recommend you to contact our DJI support team at https://www.dji.com/support?site=brandsite&from=nav for further assistance. We have a team that will do there best to check the said drone and will give out the best resolution for this issue. Just a reminder that  DJI do not recommend doing a DIY in fixing the said DJI drone to avoid further damaging the said unit. Again I am sorry for the trouble and thank you for your understanding.

I want to know how much it would be, or if you will even work on water-damaged products, before I submit the request.
Has anyone else on this forum ever had this issue?

laphlaw Posted at 12-7 20:29
I want to know how much it would be, or if you will even work on water-damaged products, before I submit the request.
Has anyone else on this forum ever had this issue?

You will need to send it in to Dji for a quote, they won't give a price without seeing the drone.

laphlaw Posted at 12-7 20:29
I want to know how much it would be, or if you will even work on water-damaged products, before I submit the request.
Has anyone else on this forum ever had this issue?

Many of us were able to rescue drones sunken accidentally in fresh water, a few only were lucky enough to get along without serious penalty. Unfortunately "bag of rice" remedy is a myth. The rice will absorb the moisture, but will also effectively hold it wrapped around the drone. A gentle fan blow is much more efficient ...

Apparently luck is not on your side this time, I'm sorry to say. Electronics and water doesn't like each other. There's no way to tell which part went bad ...  

send it  to DJI they are reasonable

I filled out one of their forms for repair, and it said that if I decided to decline the service, I would be charged $65. And it’s hard to agree to those terms, without knowing how much it will be to fix it. If it costs nearly as much as a new drone, I would just buy a new drone.

Has anyone ever dealt with them on water damage? How much did it cost you?

laphlaw Posted at 12-8 09:46
I filled out one of their forms for repair, and it said that if I decided to decline the service, I would be charged $65. And it’s hard to agree to those terms, without knowing how much it will be to fix it. If it costs nearly as much as a new drone, I would just buy a new drone.

Has anyone ever dealt with them on water damage? How much did it cost you?

I've heard of flooded drones that appeared dry after a couple of days in front of a  fan, yet did not resume normal flight until weeks later, when every last trace of humidity was finally dried out over a longer timespan.  

Don't write of that Mavic Pro until it has been left for longer, to dry completely in every internal nook and cranny in a well ventilated spot.

it's been over 2 months since it happened.. its not going to get any drier.
Did you watch the video? It turns on fine, but looks like the motors for the propellors are a bit underpowered. Any estimate on how much DJI would charge to replace, let's say, all 4 motors?

laphlaw Posted at 12-9 10:00
it's been over 2 months since it happened.. its not going to get any drier.
Did you watch the video? It turns on fine, but looks like the motors for the propellors are a bit underpowered. Any estimate on how much DJI would charge to replace, let's say, all 4 motors?

Oops.  Didn't watch the video.  Apologies for the unhelpful speculation.