Deep Cove is an arm of
Doubtful Sound, a deep indentation in the southwest coast of
New Zealand's
South Island. Along with the Hall Arm, which lies to the southwest of Deep Cove, it forms one of the two most remote parts of the sound from the
Tasman Sea, with its mouth being from the mouth of Doubtful Sound. Elizabeth Island lies close to the junction of Deep Cove and the Hall Arm. The cove is home to several notable waterfalls, notably Helena Falls and
Lady Alice Falls.