Basic:
* Aquamarine: A bluish-green gemstone.
* Aquarium: A tank for keeping fish and other aquatic animals.
* Aquatic: Relating to water.
* Aquaculture: The farming of aquatic organisms.
* Aqueduct: A channel for carrying water.
* Aquifer: A layer of rock or soil that holds groundwater.
* Aquaponics: A system of growing plants in water.
* Aquavit: A Scandinavian spirit.
Less Common:
* Aqualung: A scuba diving apparatus.
* Aqua-lunging: The sport of scuba diving.
* Aqua-aerobics: Water-based exercise.
* Aqua-gym: A gym that specializes in water aerobics.
* Aquaplaning: When a car loses traction on a wet road surface.
* Aquaplane: A water ski used for aquaplaning.
* Aquascape: The art of arranging aquatic plants and objects in an aquarium.
* Aqua-therapy: Therapeutic use of water.
* Aqualogue: A device for communicating underwater.
Scientific:
* Aqua regia: A highly corrosive mixture of nitric acid and hydrochloric acid.
* Aqua-culture: The cultivation of aquatic organisms.
* Aquametry: The measurement of water.
* Aquaporin: A type of protein that transports water across cell membranes.
Note: The word "aqua" is often used as a prefix to indicate a connection to water. There are many other words with "aqua" in them, depending on your field of interest.