We were recently approached by an engineering company with an interesting problem.  The needed a gallon of water from the bottom of a mine pit for testing.  Complicating matters, was the fact that no one had been to the bottom of the pit in over 30 years.  The haul roads that would have provided access were all severely washed out and degraded making travel to the bottom of the pit unsafe.   Initially, we thought it would be quite simple to send a drone to the bottom of the pit and retrieve some water using a standard bailer.  We did a few tests at our test range which has a small lake, ensuring that the bailer would work without being in a pipe.  After a few modifications, the drone was set.  Another problem is that drones use an enormous amount of energy while climbing.  On a typical mapping mission, this is usually done that the beginning of the flight, when batteries are fresh and full of power.  Add additional weight, and you have a recipe for disaster.   We did some additional tests to determine the maximum weight, and energy required for the trip.  Additionally, just seeing the drone – a 1000′ feet down, and determining how high it is above the water surface was also a challenge.  We opted to use two drones, one large one for the water sample and a smaller drone, with a high definition camera to give the pilot of the first drone clear visibility of bailer over the water.  It took four trips, each lasting about 10 minutes to collect a full gallon of bright green highly alkaline mine pit water.  The big bonus – the incredible video that we collected from the bottom of the pit – untouched in over 30 years.