What does "undersea" mean?

Existing, relating to, or made for use beneath the sea.

What is a synonym for "undersea"?

Common synonyms include: buried, deep sea, deep-sea expedition, drowned, engulfed, flooded.

adj

adj ·3 syllables ·Uncommon ·Advanced level

Adjective

1
Existing, relating to, or made for use beneath the sea. not-comparable
"It is not known just what action will be taken against the captain of the undersea boat."

Adjective

"A tsunami is a series of waves caused by earthquakes or undersea volcanic eruptions."

From under- + sea.