Ducks and geese do a fair job controlling various insects, including sow bugs, slugs, earwigs, beetles, and worms. Unfortunately, they don't have very good table manners.
The noise, messy droppings, and occasional aggressive posturing are bad enough, but the odor, well, you haven't really lived until you've taken a deep breath, then nearly gagged!
Bread, insects, apples, and small fish.
Their feeding damages grass, and their unsanitary droppings pose health hazards to humans and pets.
A commercial goose repellent is available, and is fairly effective in repelling geese. It tastes terrible - when the birds graze and taste the grass, they head for the nearest drink of water to get rid of the unpleasant taste.
To keep these critters out of your vegetable garden, build a fence around it. Use chicken wire which should be at least 5 feet tall. Individual plants need wire cages firmly anchored below ground.
For lakefront control, place 12" long stakes in a random pattern along the shore, then stretch wire or string in between each stake. Flag the string. This messes up their takeoffs and landings, so they leave your property alone.
To repel them, antagonize them. Random noise is a start. Break their landing habit with a cheap timer and audio tape of a couple of dogs barking, a loud horn or strobe light.