When I watch that video all I can think about is the sheer terror those poor sailors of ages past must have gone through in their wooden ships!
In some ways and by history, those wooden ships had 'some' advantages over more modern materials. Wood, especially that from old growth forests, has considerable strength along with flexibility that is lacking with metal or fiberglass materials.
Saying this does NOT MEAN that any mariner wants to test an angry sea when it can be avoided! One of our most famous naval leaders of WW2 in the Pacific was Admiral Bill Halsey, a man of decades of sea duty as well as being a licensed pilot (aviation). He commanded his fleet to 'sail' through 2 Typhoons (Pacific Hurricane / Cyclone). The conceit could be that steel ships are crewed by men of steel but the men who survived those storms had words in their diaries that argued that decision by Halsey.
As for these robotic drones bing discussed, the air-dropped 'unpowered' penetrators simply means that there is no significant stored power at the time of drop BUT it is not a permanent condition. Gravity and air can be used to spin a prop that will generate an electric charge in that drone's brief life.
As for that sea-surface drone that transmitted the video, it has solar cells to keep its batteries at a charge. Its propulsion is by the sail-shape of its top structure. The design of these 'Sail Drones' is not to have a specific destination but rather to free-roam and report what the conditions are where it is. Essentially, they are 'cheap throw-aways' that return value by their reports.