科学家们知道海洋平均有2.3英里（3.7公里）深，但许多地方要浅得多或深得多。为了测量深度，他们使用声纳，声纳可用声音导航和测距。船发出声能脉冲，并根据声音返回的速度测量深度。

1872年，英国海军舰艇“挑战者”号（HMS Challenger）号船员从海洋的许多不同区域采集了岩石、泥土和动物的样本。他们还发现了西太平洋最深的区域之一，马里亚纳海沟，绵延1580英里（2540公里）。马里亚纳海沟南端的一个区域可能是海洋中最深的地方。它被称为挑战者深渊（Challenger Deep），深达35768至36037英尺，几乎7英里（11公里）。

How deep is the ocean?

How deep is the ocean?

https://theconversation.com/how-deep-is-the-ocean-121168

How Deep Is the Ocean? - WorldAtlas

https://www.worldatlas.com/articles/how-deep-is-the-ocean.html

Any ocean depth greater than 200 meters is considered deep sea. The average depth of the World Ocean is 3.5 km. However, the deepest known part of the World Ocean is Challenger Deep, which has a depth of about 11 km. Challenger Deep is located in the southern end of the Mariana Trench, in the Pacific Ocean, 700 kilometers southwest of Guam.