I'm translating a children's story from Russian into English, and there is a phrase that I'm having trouble translating into a way that sounds natural in English.
A baby boy urinates unexpectedly and in large quantity. I have translated the phrase literally from Russian into "let up a fountain", but it sounds odd to my ear.
Однажды утром папа и мама распеленали младенца, положили на спинку и уже собирались в очередной раз с ним поагукать, но тут малыш вдруг, сам для себя неожиданно, как пустит вверх фонтанчик. Обоих родителей облил.
One morning the mother and father unwrapped their youngster, put him on his back and were about to coo at him once again, but the baby suddenly, and unexpectedly even to himself, let up a fountain. Both parents were drenched.
Can you think of a more natural way to phrase this?