We made a nice plug that seals water into your fish box but allows for easily controllable drainage. The plug is threaded and seals nicely when closed to keep your slush water cold for better icing your catch. When you're ready to drain, you can crack the plug 1/2 turn to drain water without allowing scales and other fish debris to enter your plumbing. Or, you can remove the drain ultimately to allow faster drainage and macerate any larger fish debris. Low profile flange allows for complete drainage of the fish box.