Diver's Dream™ 5.9" L x 3.9" W x 0.5" H Magnesium Rectangular Hull Plate Anode (CMDIVERMINIM) by Martyr®. Looking to protect your boat from corrosion that can occur in salt, brackish or fresh water? Then premium-grade Martyr anodes are the way to go. Pressure die-cast and made of a specialized alloy based on the US Mil Spec they offer corrosion protection and longevity unmatched by the competition. Plus, these anodes are rigorously tested in the company’s state-of-the-art laboratory, so you can rest assured of their superior quality.