Aerial Water Sampler

In one aspect, a vehicle includes an aerial propulsion system, an altitude sensor system, a water sampling system, and a control system. The water sampling system includes a water sampling extension configured to extend away from the vehicle, one or more water sample receptacles, and a water pump. The control system is configured to perform operations including: guiding, using the aerial propulsion system, the vehicle over a water source; causing, using sensor data from the altitude sensor system, the vehicle to descend towards the water source so that the water sampling extension contacts the water source; and causing, using the water sampling system, the water pump to pump water from the water source into the one or more water sample receptacles through the water sampling extension while the vehicle is in flight over the water source.