1) The well drilled for water turned out to be extremely deep.

2) The cave was extremely deep, delving hundreds of feet below the surface.

3) The emotions expressed in her poetry were extremely deep and touching.

4) The lake was extremely deep, with no visible bottom in sight.

5) His knowledge of ancient history was extremely deep, almost unparalleled.

6) The impact of the earthquake caused an extremely deep crack in the ground.

7) The scientist discovered an extremely deep layer of ice in the Arctic.

8) The character in the novel had an extremely deep and mysterious past.

9) The ocean floor in that area is known to be extremely deep, suitable for deep-sea diving.

10) The composer expressed his sorrow through an extremely deep and melancholic melody.

11) I'm sorry, but it seems like "Extremely Deep" is not a single word, but a phrase. Would you like me to provide example sentences using the word "extremely" or "deep" separately?