However, if you're asking for a more specific term for a large group of shoals, you could use:
* A school of shoals - This describes a large group of shoals swimming together.
* A swarm of shoals - This emphasizes the density and movement of the group.
* A multitude of shoals - This emphasizes the sheer number of shoals present.
Ultimately, the best term to use depends on the specific context and the desired effect.