Israel's huge new offshore gas resource offers its enemies an obvious target and gives its navy, long overshadowed by other branches of the Israeli armed forces, a big job that will require extra spending. On patrol boat 836, circling two gas platforms in choppy Mediterranean waters, Captain Ilan Lavi flipped through pictures of the possible threats: boat bombs, drones, submarine vessels, rockets and missiles. "We have to build an entire new defensive envelope," said Lavi, head of the navy's planning department who talks as knowledgeably about the financial aspects of the gas i