Yep this would have been their next problem... (since the UN doesn´t recognize the blocade. But still it would have been a lot better if they would have waited longer (at least untill they reach the blocade).
Because right now raiding a ship in international waters is called piracy under the law of sea (and there for the crew is allowed to defend themseles with all means). Because as long as they are not entering teritorial waters or at least the line of blocade they are just civillians who cruise for “fun” in international waters.
The US Coast Guard boards ships/Boats all the time in International Waters.. Ya think they would not open fire if attacked or fired upon ?????