When fighting erupted in Gaza last month and rockets rained on Israel, the men operating its navy submarine Leviathan knew next to nothing.
Submerged for a drill, only brief bulletins were relayed to them so as not to distract from their mission.
"We are by definition clandestine and, to a degree, isolated at sea. Our performance depends on our focus," a senior navy officer told Reuters aboard Leviathan during a training run.
A Dolphin's core operational crew size is 45, with an average age of 22, the senior officer said. Ten or more people can squeeze aboard, for training or deployment as frogmen.
At their homeport of Haifa, a fortified hangar shields the Dolphins from rocket strikes or hostile eyes. Crews are expected to put to sea at extremely short notice, the officer said.
Leviathan is named after the biblical whale. Dining, as elsewhere in Israel's military, is kosher.
Prayers precede Sabbath meals, with blessings over grape juice instead of wine. Purified seawater allows for regular showers and laundry by hand. A static bike, board games, and videos help the soldiers pass downtime.
Cramped quarters mean junior submariners rotate three-to-a-bed. On longer trips, some wear casual clothes, and everyone goes by first names except the captain and first mate.
There is almost no "compartmentalization" during missions. The crew is kept apprised of secret plans to create a sense of common cause, the senior officer said.