After 40 minutes on a sea bed ,  Spark is alive again !!!!!    In this story I have explained what happened. Now  I`ll tell what I did .
First of all, I washed it up with lot of tap water and when came to apartment, put it in water and left all night. After 3 days when came home from vacation, disansembled it, take off all caps on motherboard, washed firmly with toothbrush and water and alkohol. Dried with hot air, put new battery, but nothing hapened. Tried again in a week, but nothing. Dead.  Well, I said goodbue to my friend and leave it on a shelf.  Then after a week said to my self, let`s try again and miracle happened.   Old sound and leds on again! Well, all led were red.

Opened app and saw a message that is no data from battery. Bad connection. So, had to open it and try to find  a cause. And yes, battery connectors were very dirty.

After cleaning it, Spark worked like a charm !  All cameras, all sensors. One motor went hard and I opened it and cleaned of rust and sprayed with teflon.
Yesterday made a flight and Spark was like a bird again   

Hello and good day nntom. Thank you for sharing your experience on what happened to your DJI Spark and it is great to know that your DJI Spark is back up an flying. If you have any issues with the said drone in the future. Please do not hesitate to contact our DJI Support Team for us to be able to help and assists you further at https://www.dji.com/support?site=brandsite&from=nav . Have a safe and a happy flying always.

Nice

Wow. What a relief!

You were very lucky.  Just hope it doesn't fail again in the sky.

Nice to know that, fly safe

Very happy for you, well done!

Nice one - thanks for sharing

Nice work! Good luck

this is awesome news for you!!! Way to go and persever,

You are very lucky, glad that it was fine

Might sound a little ridiculous, but i am absolutley dumbfounded by how you even managed to save your spark, especially sitting in saltwater for 40 minutes. Epic save!

Thanks you all for your wishies. For seven days, I was flying and flying. Not a one problem. Actually I, for the first time I menaged to FLY ABOVE CLOUDS  and I was happy like a child!!!
Message to you all would be, Do not give up. DJI obviously did very good job. Be patient, clean it and wait.

All the best

PS  yes, clouds was very low, in the waley and I have to go to maybe only 200m to reach above

Another thing...Crosed my mind...If Spark loose power,  battery droped, maybe it was crucial. No electricity on mainboard, something to be burned out...When I opened battery, it was in really bad shape. When cleaned, what I realized when was looking at the battery board is that all connections are sealed, lacquered. All 3 cells give 4V, but flat connections from each cell are in very bad condition. I'll try to find a way to connect cells together with board again

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Great Post