An artesian aquifer is a confine aquifer containing groundwater that will flow upwards through a well without the need for pumping. Water may even spurt out of the ground if the natural pressure is high enough. An aquifer provides the water for an artesian well. An aquifer is a layer of soft rock, like limestone or sandstone, that absorbs water from an inlet path. Porous stone is crushed between impermeable rocks or clay. This keeps the pressure high, so when the water finds a hole, it overcomes gravity and goes up instead of down.