Similar to other "drone swarms" that have been reported over the past few years by both ship crews and ground observers. Noteworthy in that they are all relatively small and have not exhibited other than pedestrian performance capabilities. In one case the captain of a USN warship ordered the crew to be prepared to take a similar object under fire with small arms that are essentially glorified Nerf guns.
Interesting to note that while the crew in this video uses the expression "splash" when the object appears to hit the water, we don't actually see a splash as one would expect when a six foot object traveling at speed impacts the water. Also, no mention as to whether these objects were seen with the naked eye by any of the crew(s) on the ship(s) that reported them.