I am from Northern Ontario and so when we fly we are dodging bodies of water and marshland on all sides.
Landing sight of the Moonshot Mission:
We have yet to land right in the water, but my Byonics tracker did get fried by water when we lost the payload in the bush for five days in the melting snow (Snowday: A Canadian HAB Adventure). So we have tried to mitigate the risk through...
1) Spot Trace anti-theft device is waterproof and sent beacons while wet
2) we only set the launch date when the flight path prediction indicates that we are unlikely to hit the water
3) after the Snowday flight we put the new Byonics tracker in a milk bag for the flight and seal it around the antenna cable with elastics (in Canada we buy milk in a bag so this is just a thick plastic bag)
4) we use a PITS (Pi in the Sky) board and it was not damaged when it got wet - it does not transmit while in water but once everything evaporates data and images were still on the SD card and the tracker was just fine on the next flight
5) we use a very flat styrofoam payload shape (12" x 12" x 3") so that if the payload lands in the water chances are it will stay upright and we basically seal the bottom of the payload around the antennas and then cut very narrow slits near the top of the box for cameras since we use PiCameras with ribbon cable and the smallest hole possible for wires to the exterior sensors - we hope all of this will buy us some time while we make our way out to the payload in the lake
6) prayer, but the effectiveness of this is difficult to assess