Calcium, being an essential mineral with many important and diversified functions, plays an important role in the health and well being of the human. Marine organisms serve as an alternate source for calcium. Calcium has to be solubilized in the body in order to have the maximum benefits. The increased solubility of calcium from diet contributes to calcium absorption and bioavailability in the body. In this paper, we report various marine sources of calcium, solubilizing the calcium to improve the bioavailability and the applications of calcium as an important mineral in controlling different diseases.