I accidentally crashed my spark in a pool. I was able to retrieve it in less than a minute. Took out the battery immediately. After letting it dry for 3 days in a ziplock bag w/ dessicants, I tried to turn it on using a different battery. It managed to turn on,however, I was getting this "Battery Error" message on the go 4 app. Any inputs would be much appreciated. Thank you.

Hi, we're sorry to know about the mishap that happened on your drone. I highly recommend sending the unit into our repair facility as your drone experience water damage and the performance of it may be affected causing further damage to the drone in the future. Please sync your flight records using the DJI GO 4 app. For additional information, for the sake of security,  we indeed don't repair water damaged drone. Because aircraft consists of a large quantity of sensitive electrical components, after it is water damaged, electrical components may be corroded, thus affecting its stability and security. Through the related tests, the repair of water damaged units needs to replace all the relevant components, and it is possible that the cost of repairing a water damaged drone is far higher than buying a new drone. Therefore, we advise that water damaged units are ineligible for a repair service. Thanks for your understanding and cooperation. If you wish to contact our support, kindly see the link below.

www.dji.com/support

If you landed the dji spark in water you just have to replace it.  It is damaged too much to fix.