This is a theme puzzle with the subject stated below. Find the listed words in the grid and when you have completed the puzzle, there will be letters left over. They spell out the alternative theme of the puzzle.
Inland water was
Solution: 27 letters
Albury Ashburton Avon Barwon Botany Bay Cadell Canoe Carp Cobram Colo Cox Daly Dam Darling Esk Finke Fish Flow Genoa Hay Hull Hume Lake Macleay Mary Maze Moama Mud Nymboida Oar Onkaparinga Orara Ord Paroo Peel River Roper Run Sand Shark Ski Snowy Sun Surf Swan Swim Tides Tully Warragamba Waters Weir Wet