Synonyms of the word

undersea

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

submarine

• adj. Undersea.
• adj. Hidden or undisclosed.
• adj. (baseball) Of a pitch, thrown with the hand lower than the elbow.
• n. A boat that can go underwater.
• n. A kind of sandwich made in a long loaf of bread.
• n. (baseball) Pitch delivered with an underhand motion.
• n. Any submarine plant or animal.
• n. (informal) A stowaway on a seagoing vessel.
• v. To operate or serve on a submarine.
• v. To torpedo; to destroy with a sudden sneak attack.

subsurface

• n. Something that is below the layer that is on the surface.
• n. (countable, mathematics) A surface which is a submanifold of another surface.
• adj. below the surface.