Hello Piku23,
When one doesnt masturbate for sometime, nightfall is the outcome. See it works like this, if a tank has water and water fills up in the tank, the tank overflows , in the same way when there is build up of semen, semen comes through nightfall. Semen can be thick, or watery, it is varied.
https://lovematters.in/en/our-bodies/male-body/is-masturbation-making-my..., read this link to know that masturbation has nothing to do with semen being watery. Watery semen has the same amount of sperm as in thick semen. All the best.