The vessels don’t have to be boarded - just sink them as they come in range ...
I would not be surprised to discover that Israeli operatives have already infiltrated the groups who are planning this ‘flotilla’, and are likely to be on board some or maybe even all of the ships. So, sinking them would probably be counterproductive. For all we know, the boats may already have been “boarded” before a single interception has been attempted.
Have agents aboard disable a couple of the boats and the rest will have to tow them home.
The vessels dont have to be boarded - just sink them as they come in range ...