Dual core mattress

A dual core mattress, comprising:

• a) a removable upper cover having an upper surface, a lower surface, and an upper cover zipper portion, wherein the upper cover zipper portion extends around the lower periphery of the upper cover on a lower peripheral edge of the upper cover and includes downwardly extending zipper teeth;
• b) an upper mattress layer below the upper cover, the upper mattress layer having an upper surface and a lower surface;
• and
• c) a bottom mattress layer below the upper mattress layer, the bottom mattress layer having an upper surface and a lower surface, wherein the bottom mattress layer further comprises:
• (i) a waterproof material on the upper surface of the bottom mattress layer;
• (ii) an upper positioning zipper portion attached to an upper strip tape extending around the periphery of the bottom mattress layer at an upper end of the bottom mattress layer, the upper positioning zipper portion comprising upwardly extending zipper teeth;
• (iii) a lower positioning zipper portion attached to a lower strip tape extending around the periphery of the bottom mattress layer below the upper strip tape, the lower positioning zipper portion comprising upwardly extending zipper teeth;
• wherein the upper cover zipper portion can be removably secured to the upper positioning zipper portion when the upper mattress layer is positioned on the upper surface of the bottom mattress layer, and wherein the upper cover zipper portion can be removably secured to the lower positioning zipper portion when the upper mattress layer is positioned on the upper surface of the bottom mattress layer, thereby allowing the dual core mattress to be have two different vertical heights.