Shoal (noun)

1. A shallow area of water, especially one that is a hazard to ships.
2. A large group of fish or other sea creatures.
3. A large area of shallow water or sand.

Origin:

The word "shoal" comes from the middle english word "scholle" and old english "sceolh", both of which are related to the germanic base "skel" meaning "to divide" or "to separate".

Examples:

1. The boat hit a shoal and got stuck.
2. The shoal of fish was so dense that it looked like a moving carpet.
3. The swimmers were warned about the dangerous shoals.
4. The shoal of fish was swimming near the surface.
5. The diver saw a shoal of colorful fish.