If you have control over the water (can drain the pond and fill it back up) and it's not too deep, then corn would be my first choice to plant and leave standing then flood for the season. If you can't control the water, then something like Japanese Millet around the moist edges would be something simple and easy to plant. If the farmer helps you out, you could disc around the pond and plant millet, sorghum, or rice. Smart weed is another choice that would be a perennial that once established you wouldn't have to bother with again. Bear in mind that geese like a clean bank around a pond for lounging and loafing, so if you are able to have a grassy area or clean soil on one side, right down to the water line, the geese like that.