French GruntHaemulon flavolineatum
You can't be snorkeling on St. John without seeing some French Grunts. They are one of the most populous species you'll see in these waters. You'll see juveniles through the adult stages of development (as pictured). The adult fish are a bluish white color with yellow stripes. They school in groups, resting during the day in sheltered areas of the reefs and shorelines. This is the only grunt that has diagonally slanted stripes on his side. The French grunts you'll see while snorkeling will be older juveniles or sub adults and will be about 4 inches in length.