There's no marines onboard a destroyer, and no one is shooting anything that hasn't shot first when you're in that area, it's full of Navy training platforms and civilians.
Based on the flight times and 100 mile flights ~100 miles off the coast and the investigated boats in the area...they couldn't be small. At least not with current consumer battery technology. Maybe if they were launched by a sub?
There's a youtuber that has a multi-hour autonomous drone, but it's solar powered and this was at night.