submarine
noun
[ ˈsʌbməriːn ]
• a warship with a streamlined hull designed to operate completely submerged in the sea for long periods, equipped with a periscope and typically armed with torpedoes or missiles.
• a sandwich made of a long roll typically filled with meat, cheese, and vegetables such as lettuce, tomato, and onions.
submarine
adjective
• existing, occurring, or used under the surface of the sea.
• "submarine volcanic activity"