a shade of blue tinged with green
"The swimmer dove into the cool aqua water of the tropical lagoon."
The compound water.
Of a greenish-blue colour.
"The swimmer wore an aqua swimsuit that perfectly matched the turquoise water."
In plain English: Aqua means something that is blue-green, like clear ocean water.
"The swimmer dove into the cool aqua water without hesitation."
The word aqua entered English through Middle French as a learned borrowing directly from the Latin term for "water." It is considered a doublet of other water-related words like ea, which also trace their roots back to the same original language.