The malarial mosquitoes thrive in pools of stagnant water in the tropical swamps.
Advanced English Dictionary
+adjective 1 stagnant water or air is not moving and therefore smells unpleasant: a stagnant pond / pool + Few fish survive in the stagnant waters of the lake. 2 not developing, growing or changing: Major new investments are aimed at reviving the stagnant economy. + a stagnant population + The housing market has been largely stagnant over the past few months.
Random quote: The best thing in every noble dream is the dreamer...: Moncure Conway