A polymer composition that comprises an olefinic polymer, a flame retardant that includes a halogen-free mineral filler, and a compatibilizing agent is provided. The halogen-free mineral filler constitutes from about 20 wt. % to about 80 wt. % of the composition. The composition may exhibit a degree of water uptake of about 5 wt. % or less after being immersed in water for seven days at a temperature of 23° C.