Finding Relics on maps with Fish

Is there some trick I'm missing here?

I'm going for a relic victory, I've found most of them, but it seems there's always one relic off on the coast that's being hidden by fish.

I can, and do, cycle through my map types/colors and eventually find them, but I feel like there's some way to catch them that I'm missing that doesn't involve manually perusing every inch of coastline to find the one(s) I missed.