undersea

[ uhn-der-see ]

/ ˈʌn dərˌsi /

located, carried on, or used under the surface of the sea: undersea life.

underseas.

Origin of undersea

First recorded in 1605–15; under- + sea

Think advanced unmanned vehicles, all-aspect, broadband stealth, and undersea warfare.

The Pentagon May Finally Have a Plan to Keep America on Top |Bill Sweetman |November 3, 2014 |DAILY BEAST
The artifacts came from undersea dives and excavations from the area, which has been inhabited for at least 3,000 years.

Israel’s Tiniest Breakaway State |Nina Strochlic |June 12, 2014 |DAILY BEAST
All went well with Johnny on his undersea photographing trip until he had reached the fifteen-hundred-foot level.

Sign of the Green Arrow |Roy J. (Roy Judson) Snell
The death in that undersea channel was deliberate and unhurried, and the imagination had free play.

Kastle Krags |Absalom Martin

On a sloping downward course, they sped along like undersea rockets, their ion jets functioning perfectly.

Tom Swift and the Electronic Hydrolung |Victor Appleton
Women, vague in the orchard under-shadow, are picking the lemons, lurking as if in the undersea.

Sea and Sardinia |D. H. Lawrence
So passed the bulk of Germany's undersea fighting strength into the hands of Great Britain and her allies.

The Boy Allies with the Victorious Fleets |Robert L. Drake

undersea

/ (ˈʌndəˌsiː) /

below the surface of the sea