looking and listening carefully

concentrating

going a long way down from the top

extending very far, usually down

extremely busy with and interested (in an activity, book etc)

preoccupied; attentive to

(of looks) eager; earnest; (of a person) having, showing, serious and constant desire or attention

determined, resolute

so deep in thought, so carried away by feelings, that one is unaware of other things

absorbed, fascinated

that has sunk; (made) lower than the rest of the surface

depressed, hollowed; submerged

below the surface of the water

under the water's surface