Like the others say, it will depend on the breed and conditions. A good way of increasing egg production if it ever drops off, is to put them into an enforced moult. After moulting, they can be re-entered into a laying pattern and therefore begin laying more eggs.
It would be good to find a shallower basin that the chickens will not drown in, if they were to wonder in. A couple of inches of water is sufficient enough for ducks to be able to dunk their heads in for cleaning, whilst not endangering the chickens through a risk of drowning.
I'm a new member here, so I just wanted to say Hi :)
(1) Are you new to chickens / when did you first get chickens?
Unfortunately, I have never reared chickens. However, I am a farmer and geneticist for a large duck breeding company, with experience in the entire process of hatching, rearing...