Purple sea urchins are found intertidally down to 10m.  When found further in depth they tend to stay where there is plenty of Macrocystis pyrifera availible.  They are normally found in bunches during lower tides.  They can't survive outside of the water, so they must retain water by staying in the mid to low intertidal zones.  To prevent loss of water, they burrow holes into rocks and crevices.  They also use their tube feet to attach rocks and broken shells to keep moisture in.  Purple urchins can be found from Cook's Inlet, Alaska to Isla Cedros, Baja California.