Neap tides happen in the third and first quarter of the moon phase, when the moon appears to be half full, this is because of the position of the moon and the gravitational force of the moon attracting the tides along with the gravitational force of the sun, tha causes high tides on new, and full phases, but the third quarter and first quarter, the moon makes a 90º line with the solar gravitational forces, cancelling out both forces making it low tide or neap tide.