A lot of zombies at night.

I have found that the previous update there was a problem with drowned spawning and so I plugged up all the ground level aquifers, but by doing that I came into a situation that now I'm getting a lot of zombies . It's not the other hostile mobs it's just zombies, and it's not near a village (zombie siege). They will come in groups sometimes. I killed off a group by a beach, about 4 of them, started walking turned around and I saw like 5 more take there place. Any pictures I would take would be bad since it's on the Xbox but if I need to then I can. This is my first but report so sorry if I leave stuff out.