Pull the battery out of the drone and set it aside somewhere safe and fireproof because lithium batteries can become unstable when damaged and often burst into flames. Also, the more time that your drone has power applied to it, the more damage will be done.
Great! Now, let’s get on with our article.
So, your drone has crashed into a body of water; a lake, the ocean, a swimming pool perhaps. The type of water does matter. You probably weren’t given a choice, but landing in fresh water is way better than landing in salt water. Salt water is highly corrosive and electrically conductive, so the chances for every kind of harm are a lot higher if you land in the ocean than if you land in a lake.
Let’s talk about the major components and the potential risk:
- Main Board and Circuitry
Water is electrically conductive (salt water extremely so). So dipping your drone into water is like creating a thousand little short circuits all over the circuit boards. Sometimes you get lucky and nothing bad happens. Sometimes you blow up some circuitry (the motor speed controllers are extremely vulnerable since they are high-power circuits).
Modern brushless motors, like those on DJI drones, have almost no moving parts. There’s just a single bearing which, if properly cleaned up, might be just fine.
- Gimbal Assembly
The gimbal assembly has a couple of key rotating parts, including variable resistors which provide feedback on how far the motors have rotated the arms. The number one enemy here is corrosion. If you got it out of the water quickly enough (and got the salt off of it by rinsing in alcohol) you might be ok.
Depending on how deep your drone sinks, and how long it stays, water can force its way into the camera and cause condensation on the lens and the sensor. This could mean that you’ll need a new camera.
The safest thing to do with the battery if it gets more than a quick dunk is to send it to your local electronics disposal center. A battery failure often includes a fire and sometimes an explosion. Having this happen in flight is especially bad.
Once the battery is removed, the next step is to stop the corrosive action of the water and any salts in it. We recommend rinsing the drone in isopropyl alcohol (rubbing alcohol) that you buy at the drug store. Isopropyl alcohol is rather inert chemically and it absorbs water, so everywhere it gets in your drone you will be replacing something bad (water) with something less bad (alcohol).
Next, you need to get the alcohol and remaining water out. This involves disassembling the case and removing the flight controller from its enclosure (if that’s how your drone is built). Then everything goes in a warm dry place, with circulating air, not over 110 F.
While you have it disassembled, you also need to check for mechanical damage. Hitting water hard can be almost as bad as hitting the ground. Also, many water landings are really secondary crashes, having hit a tree or something else first.
Spin the motors by hand to make sure that they rotate freely. Do the same with the gimbal components.
When everything is nice and dry, and no longer smells like alcohol, you can put it back together.
Get a fresh (uncrashed) battery and insert it. Press the power switch but be ready to yank out the battery the moment you notice anything unusual (smoke, funny smell, weird behavior, heat, strange sounds). If anything out of the ordinary happens, don’t go any further; you could wind up doing a lot more damage. Send it to a professional for repair. They have better equipment and have seen a lot of crashed drones than you have.
If that’s all good, then let it power up and check it out with your controller to make sure there are no error conditions. Make sure that the camera gimbal rotates properly. This is now your first chance to see the picture from the camera. Do you have a picture at all? Is it nice and clear? Or foggy?
Next go through the IMU calibration procedure to make sure that the flight computer is still working properly. Then do a compass calibration.
If you have a Mavic Pro or Phantom 4, also do the obstacle avoidance calibration just to make sure that those cameras were not damaged. Issues with this system can cause sudden altitude drops, which can cause you to crash into things.
If everything checks out, then you are ready for a simple test flight. Low altitude hover, check for stability. Check each control to make sure that all 8 positions (left, right, etc.) work as expected.
If you got this far and everything is working, you’re pretty lucky. Just be careful to fly your drone very conservatively over the next few flights to make super extra sure that there isn’t some latent damage that’s going to cause it to drop out of the sky.
Hope this helps, and happy flying!