An island in the northwestern part of the Zadar archipelago. The highest elevation is Sridnj (185 m). The karstic ridge divides into two lower parts to the southeast. The largest bays are Dumbocica and Kablin on the southern coast and Hrvatin on the northeastern coast. The only settlement is Sestrunj. The remains of an lllyrian fort and stone mounds have been discovered on the island.
Sestrunj's harbour with three small piers lies in the Kablin Bay. The depth of the sea is 2.5 in the harbour and 2 m on the outside of the pier (breakwater). The bay is exposed to southeasterly winds. The anchorage protected only from the bora is located 400 m east of the harbour.
The northern harbour lies in the Hrvatin Bay and is exposed to northerly winds. Boats can moor behind the breakwater at a depth of 2 m or at the knee-shaped pier at a depth of 1 m. There is a launch ramp.
The Dumbocica Bay is exposed to southerly winds and provides anchorage at a depth of 8 m. Small boats can berth at the southern tip of a small pier at a depth of 1.5 m.