I'm glad the boys are safe! This is something that was bound to happen eventually and we've seen recent videos of this use and many others in advertising. I think dropping floats from a some is a natural use but it will be interesting to see if some of the other ideas survive.
Yes, I've seen the video where Casey Neistat hangs off a drone in ski gear. But to attempt a rescue, the drone is pulling against somebody who isn't trained (more movement means harder to stabilize). You're also fighting against the ocean, so you're going to need extra power to pull the person against the waves, at least until you get them plucked out.
As mentioned elsewhere in this thread, the drone will need to operate quite a bit higher up to stay safely clear of water and heavy spray, so the person would be at the end of a much longer rope, and a longer rope means the system is a longer "pendulum", which again means it'll take more energy to stabilize it.
An ocean rescue is going to happen on a warm day, whereas the Casey Neistat video was done in cold, dense air where drones are more efficient.
I would not be surprised if it takes an order of magnitude more energy, at the drone, to pull a person out of the ocean that it takes to lift a calm person on dry land. That's a big hill to climb.
Is a terrific idea in paper, but there are serious obstacles to solve. There is a potential problem in using a long swinging rope attached to a powefull engine in a beach with thousands of people looking. Ropes at high speed can cut the skin. Even worse, you do not need to apply a lot of force to suffocate or break the nek of a children.
In case of severe bad weather could work, sometimes. Ropes attached to a heavy engine that could crash and sink in seconds can be very dangerous in water.
