Bored ducks?

[Runner duck mom]

Has anyone got any ideas for older ducks? I have 2 with a fair sized pond and not much area around the pond but they can walk all the way round and there's plenty of room for both of them to sit in each corner plus their little house with food. Every morning I feed them a green treat (sprouted lentils, spinach etc) by throwing it in the pond but they seem bored. I don't know if that's even possible but hey any advice?

I'll use a Tupperware container or big zip lock bag, fill with water and add a handful of treats and freeze into a big treat cube (found that idea on this site .
They also like to play with the sprinkler or hose set to the shower setting...they bite at the water, it's hilarious!