The swimmers passed over an shoal of bass as they jumped off the escort boat.
noun - Shoal is a landform within or extending into an open body of water. Occasionally called a sand bar, shoals are typically composed of sand, silt or small pebbles. Shoals are characteristically long and narrow (linear) and develop where a stream or ocean current promotes deposition of sand or granular material, resulting in localized shallowing (shoaling) of the water. Shoals can appear in the ocean, sea, around a barrier island, in a lake, or in a river.