"Fish don't think/'Cause fish know everything."

If we make scuba diving, the sea seems a world of silence.

But it's a deceptive view.

Fish are not that smart and …they do speak.

In fact, water transmits sounds better than the air and while light penetrates just to 300 m (1,000 ft), below this depth there's total darkness and the inhabitants of the depths use sounds to ..."keep in touch".

Abyssal fish employ sounds for echolocation, in order to detect the relief of the bottom.

Amongst the sea dwellers, people are familiar with the song of the whales, that can be "heard" to 80 km (50 mi) away and the humpback whales for example can sing at intervals of 20 minutes for hours.

Cetaceans (whales and dolphins) are also known for their ultrasound echolocation: they emit sounds at 150 kHz that propagate till 3 km (1.6 mi) away, but which cannot be heard by the human ear.

In fact, ultra-sensitive submarine microphones can record, in the sea water, rustles, cracks, gasps, gnashes, bangs, sizzles, drumming sounds, ship whistles, croaks, snores.

Researches revealed how fishes produce sounds. By gnashing the front teeth emit sounds the seabreams (Sparidae), pufferfishes (Tetraodontidae), porcupinefishes (Diodontidae), sunfishes (Molidae); mackerels (Scombridae) employ the pharyngeal teeth.

Triggerfishes (Balistes), sticklebacks (Gasterosteus), and surgeonfishes (Acanthurus) emit sounds by rubbing their spines.

Clownfihes use their jawbones to emit their clacking sounds.

Some fishes have muscles that produce vibrations by their contractions. These muscles can be found on the walls of the swim bladder, like in gurnards (Trigla), dories (Zeus), toadfishes (Batrachoididae), shark catfishes (Pangasiidae) or armored catfishes (Callichthyidae) (which emit chirp like sounds).

Fish calls can have a social meaning (like in herrings) of "gathering", "danger", or "change direction", or can be territorial, like in clownfishes (Amphiprion).

Seahorses (Hippocampus) emit mating calls.

Croaker males (Sciaena) make drumming-like calls to chase away rival males during the mating season. Similar drummings are emitted by the toadfishes (Opsanus).

Gurnards scare off predators with their grumbling calls.

Pisara (Moenkhausia) - a fish of just 12 cm (5 inch) from the Amazon - emits elephant-like roars, while curbinatas (Plagioscion), also from Amazon, produce shots-like sounds.