"Intelligence Under the Sea: The Clever Behaviors of Cleaner Fish and Octopus"

The smartest fish in the world is a subject of debate, as intelligence can be difficult to quantify in fish. However, some species are known to exhibit complex behaviors and problem-solving abilities.

One example is the cleaner fish, such as the bluehead wrasse. These fish provide a cleaning service to other fish, removing parasites and dead skin. They have a complex system of communication with their clients and are able to remember the "regulars" among them.

Another example is the crows of the sea, the octopus, which are known for their intelligence and problem-solving abilities. They have been observed using tools, escaping from enclosures, and even exhibiting behaviors indicative of play.