UAVs can carry cargo, some of the very tiny UAV units can hold up to 11 lbs. Which is not much, however. A one-way UAV could fly over a river that is used for transporting troops and supplies by your enemy via hydro-craft, which can hover over regular water. These mines would normally be set by Navy Seals, by using small robotic units we can save the risk of life unless it is totally necessary.

Now then a composite or Composite & Foam UAV construction carrying several saucer shaped "Track and Field Discuss Style shaped" lightweight floating mines would be of significant value. If the UAV broke into parts upon water landing the pieces would be scattered across the river is various shapes and float like debris on water. Each component would have a small by high impact explosive on it.

The UAV would fly down the river and drop the discusses and then crash into the water or as it ran out of fuel thus breaking into parts made up of the same, start shedding pieces of its airfoils, emphanage, fuselage, etc and the final pieces dispersing upon impact. A series of these type units UAVs, such as 100 of them could literally stop travel on the waterways of a country like North Korea. You see if the UAV was painted similar colors to the water or the type of debris in the water they would not be detected until unfortunately it is too late, upon impact and detonation.

Once fast ground transportation over these water ways was stopped the logistical flow would prevent the hover craft from delivering food, water, supplies, ammo and any other necessary logistics to the front lines, including combatants. If a hovercraft did not have the mines cleared they would be inoperable and explode losing the craft, cargo and people and blocking such channels, rivers, streams or canals. This entire scenario can be accomplished by GPS-GIS satellite pinging and routing well within the parameters of autonomous flight. Thus the army, which moves on its stomachs would not be able to move. If the debris were to be fished out of the water it could be done easily, but the time consuming methods using non-magnetic materials would mean a fishing net and possible explosion on contact meaning the devises would need to be fished out one by one and only one per netting. If you miss one which re-enters the water flow then it would be flipped up by the wake or airflow or caught up underneath the craft during operations, detonate and sink the craft immediately or disable it and render it useless and in the way of logistical flow.

With small devices used it would be very human, because it simply renders vehicle un usable forever. The cost is very little considering you prevent your enemy from even fighting a war. They are simply less their most important infrastructure, their waterways, in essence their highways for moving logistics.

The cost to us to fly a few hundred or thousand UAVs is insignificant in the over all scheme of things really. You see UAVs are an excellent tool when used strategically. Floating mines of high yield and low weight explosives is really a good use of funds for limited wars, to prevent your enemy from fighting and allow them time to reconsider their options without hostility or enraged miss-calculations leading to many lives lost on both sides, mostly theirs. Model Airplanes saving lives, sure why not? What do you have to lose, these units cost little to produce and deploy.