Technically, there's nothing to stop you from doing so. You could certainly use the same material. But in practical terms, using the same test becomes problematic. It depends on what kind of fishing you're doing. You might do just fine fishing off a dock where the catches are usually small, but in general, sea angling rigs are considerably heavier than freshwater angling rigs. Fishing line needs to be stronger to account for things like beach casting leads, large lures, and, of course, bigger fish.