undersea

It is not known just what action will be taken against the captain of the undersea boat.

1920, George M. Battey, Jr., 70, 000 Miles on a Submarine Destroyer, Webb & Vary Company, page 133

"You're right!" she cried. "I'm sure you are." Twenty reasons come back. An undersea tunnel to the little island.

1923, The Saturday Evening Post, G. Graham, page 58

The Sediment (SNAP-7E) Density Meter (an underwater rocket) has been developed to investigate to an ocean-bottom depth of 11 sedimentary feet. Sea Lab I, the Navy’s new undersea laboratory, complete with observation porch and garage, should become safe to operate at the 200 foot level.

1966, Robert B. Thomas, The Old Farmer's Almanc, Yankee Pub, page 44

The bull kelp forests off Northern California are sometimes spoken of as the redwoods of the sea. And like the redwoods, these forests are in danger. In less than a decade, these otherworldly undersea landscapes, lush with life, have all but disappeared along 200 miles of coast north of San Francisco's Golden Gate Bridge.

2022 April 30, David Helvarg, “Climate change threatens another California forest, this one underwater”, in The New York Times, New York, N.Y.: The New York Times Company, →ISSN, →OCLC, archived from the original on 17 Aug 2025

The Channel Tunnel is the longest undersea tunnel in the world, with this section being 38km (23.6 miles) long.

2022 December 28, “The essential Eurotunnel”, in RAIL, number 973, page 59