You can get fishnet fabric at Walmart and also large chunks of styrofoam which can be cut in the shapes of buoys, starfish, weights, etc. Use red or green for the buoys, tan and black speckles for the starfish and grey for the weights. You might also be able to get large pieces of styrofoam at a Home Depot or Lowes. I realize these are not cheap solutions. Are you anywhere near water? If so, check with local marinas, the local coast guard auxiliary, or boat repair/manufacturing shops for anything they might be willing to loan in exchange for a program credit. Good luck! You can paint cardboard boxes to look like wooden crates. For barrels, check with a local winery.