The poem opens by describing the shark in terms of being rather unconcerned and lazy as it glides through the Maldive Sea off the tip of India. This description is placed in opposition to the real subject of the poem, the thin blue pilot-fish that actually swims inside the shark’s mouth whenever it senses the approach of a predator.
It is there inside the larger fish’s mouth that a strange symbiotic relationship develops. The shark’s mouth is about as safe a place as can be from other predators and the next few lines paint a portrait of how the inherent danger of lurking among rows of sharp teeth helps to ensure the smaller fish is free from fear of harm.
The final few lines reveal what the shark gets in exchange for this symbiotic leasing agreement to a perpetual tenant. In its escape into the mouth, the pilot-fish’s flight to safety from approaching predators becomes an alert of the presence of a meal to the lethargic, dull dotard of a shark. The implication being that the shark is either too dumb or too lazy to recognize this approach on its own. Since the pilot-fish does partake of the food that the shark eats in this way, the implicit question raised is one of complicity. Does the pilot-fish bear responsibility for the attacks on the predators since it does not eat it, but is only trying to hide or is the pilot-fish innocent?