Ocean front environments are potentially the most hazardous of all. The salt can quickly corrode thin aluminum tags. Additionally, the successive cycles of wet/dry conditions can excelerate crazing andcracking. Fiberglass signs, however, seem to hold up very well or thick or anodized aluminum markers can be used with good results. Navy ships, for example, use anodized aluminum for their markings.
 
 

Aluminum pole marker corrodes and actually "evaporates" next to sea. Make sure parts are thick enough to withstand corrosion.

Sign deteriorated within five years near ocean spray environment.