I've watched some videos showing UNREP and they're fascinating. It takes a lot of skill to keep the ships parallel. There was a collision earlier this year between the resupply ship and the recipient.

Analysis:

https://www.youtube.com/watch?v=zSYl9y3e944

Also, the Navy is using Ospreys to resupply submarines at sea because they have the range and helicopters don't.

> Also, the Navy is using Ospreys to resupply submarines at sea because they have the range and helicopters don't.

Afaik, modern submarines handle terribly on the surface, so I imagine direct ship-to-ship UNREP is rare. Also, too much cost risk from a collision.

Per YouTube, it's mostly vertical replenishment. Helicopter for short range. Osprey for longer. Floating pallets pushed out of the back of a C-17 at max range.

I'm sure the packing is intricate for something that's going to be air dropped, then floating, then has to be broken down on an unstable floating platform and conveyed inside through small ports!