Those waters only go to Egypt and Gaza and Israel had UN permission to blockade Gaza. The Flotilla refused to go to Egypt so Israel had no other choice but to inspect the goods. If you saw the video, the Israeli soldiers were lynched by a mob. Five other boats accepted Israeli inspection.
Israeli ambassador to U.K.: Elements of left 'in denial' about 'disease' of anti-Semitism (Haaretz)
from the article: U.S.: UN council rushing to blame Israel for Gaza flotilla deaths