By establishing a direct electrical current between electrodes in an electrolyte like sea water, calcium carbonates, magnesium hydroxides, and hydrogen are precipitated at the cathode, while the anode produces oxygen and chlorine. Recent experiments have demonstrated in part the feasibility of using the electrodeposited minerals as building materials for a wide variety of purposes, including the construction of artificial reefs. Several of these experiments are described and some implications for marine building technology are discussed. .-. ..- .