You need to go with something that resembles the native "bushes". And, if possible and legal, use the native bushes themselves. Nothing handier than a stout bush axe for this. A few quick swings and you'll have enough to cover the boat.

If this is not possible, then you can use fast grass, or some other type of woven palm grass. And I am sure you likely have the ubiquitous palmetto bush around, these are great because they are sturdy and weather proof. Also readily found in marshy areas. If all else fails...raid the office supply store and buy up some ficus trees!