The name Tasman Bay is generally applied to the broad triangular indentation, approximately 47 miles across and 35 miles deep, in the northern coast of the South Island between Separation Point and D'Urville Island. The bay was discovered by Tasman in 1642, but was not named.

Tasman Bay, located at the north end of New Zealand's South Island, is a relatively shallow body of water compared to the open ocean. Its depth varies across the bay, but it generally averages around 20 to 50 meters (roughly 65 to 165 feet). The bay is characterized by a gently sloping seafloor that reaches its maximum depths as it opens up toward the Cook Strait and the Tasman Sea. Because it is not exceptionally deep, the bay is highly productive for commercial fishing and aquaculture, particularly for scallops and green-lipped mussels. The shallow nature of the bay also means that the water temperatures can fluctuate more significantly than deeper oceanic waters, making it a popular spot for recreational boating and swimming near the Abel Tasman National Park, where the turquoise waters meet the golden sandy beaches.