The ship was reportedly at anchor. One of the characteristics of ships is that they are mobile. What if it decided to move. Under whose control are they?
If you put a moveable obstruction at various points in the net takeoff flight path you have a large number of scenarios to think of.
If you just kick the tyres and light the fires and blast off, if anything goes wrong, the FAA, victims lawyers, and last but not least Pprune spotters, will all have the benefit of hindsight as they drag your decision over the coals.