The durability of ecological concrete in a marine environment was studied. Specimens of a six-year-old submerged ecological concrete from a breakwater located in the East Mediterranean sea were analyzed for their biological carbonate deposition cover, chloride effective diffusion, carbonation, and mineralogy. About 57% of the surface was found to be covered by biogenic-deposited carbonates. The effective chloride diffusion coefficient and the carbonation rate were found to be reduced proportionally to the biogenic-carbonate cover. Most of the aluminates were found in non-crystalline minerals. No evidence of a sulfate attack was found.