Remember, geese and goslings need to be able to rinse their bills and eyes in water. So your water level shouldn't be too shallow.
Also, they love bathing and they're good swimmers. As long as they're able to get out of the pool, the water level isn't important. On warm days you can let your goslings play, bathe and swim in the water, you just have to make sure they're able to dry off afterwards without getting too cold. Goslings raised by their parents will be almost waterproof from the static of rubbing against their parents' feathers, and they'll keep warm under their parents. Your goslings are not that waterproof and can get cold when all their downs are wet.
One of the problems with keeping chickens and geese together is that geese love and need plenty of water, whereas chickens tend to drown in it.
Also, they love bathing and they're good swimmers. As long as they're able to get out of the pool, the water level isn't important. On warm days you can let your goslings play, bathe and swim in the water, you just have to make sure they're able to dry off afterwards without getting too cold. Goslings raised by their parents will be almost waterproof from the static of rubbing against their parents' feathers, and they'll keep warm under their parents. Your goslings are not that waterproof and can get cold when all their downs are wet.
One of the problems with keeping chickens and geese together is that geese love and need plenty of water, whereas chickens tend to drown in it.