sentences:  These boats were part of the closure imposed on the shores in order to prevent Jewish immigration.In Haifa Yohai Ben-Nun led the operation and in Jaffa, Yossi Harel and Zalman Cohen did, after a briefing by Yitzhak Sadeh.In both cases the sappers arrived in boats, dived under the British boats and attached explosives with a delay mechanism to the boats.