If U've opted for International Law,help us look at the illegality of what Israel did

This matter falls under 'jus ad bellum'.Isn't it?It is a violation of UN Charter Article 2(3) which says that"All members shall settle their international disputes by peaceful means only" and also a violation of Article 2(4) which says"All members shall refrain in their international relations from the threat or use of force against the territorial integrity and political independence of any State."
But Israel has a certain way to respond to its unending list of violations.It says it is only acting in self-defence,citing the much abused Article 51 of UN Charter.

That brings us to one troubling question...Where do you draw the line between "Use of Force" and "Act of Aggression"????Its important to know that because use of force can justify action under Art 51 but aggression is unjustifiable.

Two,I would like to know whether 'jus in bello'(the Geneva and Hague Conventions)applies in this case???(considering the fact that they relate to armed conflict and this sure doesn't qualify as armed conflict.)

Lastly,when Israel intercepted the flotilla ships,it entered into Gaza's waters.What does the Law of Sea say about that?How bad is it for a country to penetrate another country's territorial waters???

I would appreciate an informative reply