French Grunts (Haemulon flavolineatum) and Blue Striped-Grunts (Haemulon sciurus) are quite common and can be seen on nearly every shallow reef dive in the Caribbean. Grunts are so named because they can produce a grunting sound by grinding their teeth together and amplifying the noise with their air bladders!
The main photo above shows French Grunts schooling together as they are typically found on a dive. The key to identifying a French Grunt on a dive is to look at the stripes along the side of its body. The first few rows of stripes run lengthwise down the fish's body, but the lower stripes are diagonal.
The lower left photo shows a Blue-Striped Grunt. The Blue-Striped Grunt has obvious blue stripes that may appear to be outlined in a darker blue upon close examination (if a diver can get the fish to stay still long enough!). The easiest way to identify a Blue-Striped Grunt is by it dark, brownish tail fin and dorsal (top) fin.
More scuba diving photos: