National Freshwater Fishing Hall of Fame has a 143-foot muskie fish building. It's lower jaw is an observation deck.

The Ozark cavefish (Amblyopsis rosae) is a small subterranean freshwater fish native to the United States. The fish has no pelvic fin; the dorsal and anal fins are farther back than on most fish. It has only rudimentary eyes and no optic nerve.

Shallow waters will sometimes get too hot, forcing one fish to make a break for the shore. The tiny mangrove rivulus (shown above) avoids neurological damage from hot swamps by escaping to land. Retreating to land allows the fish to cool down through a process called evaporative cooling, which is akin to human sweating but using water from the environment. Previously, scientists had suggested that the fish, besides simply escaping hot water, might be taking advantage of evaporative cooling.

Source: http://rsbl.royalsocietypublishing.org/content/11/10/20150689 ...

The hairy frogfish (Antennarius striatus) is a marine fish with spines resembling strands of hair - and it can change color. This small fish grows up to 22 cm (8.7 in) long, and has a rounded, extensible body. Its large mouth is forwardly extensible, allowing it to swallow prey as large as itself! The coloring of its body is extremely variable because individual fish tend to match their living environments.

Frogfishes have the capacity to change coloration and pigment pattern, taking only a few weeks to adapt. The dominant coloration varies from yellow to brownish-orange, passing through a range of shades, but it can also be green, gray, brown, almost white, or even completely black without any pattern. Body and fins can be marked with roug ...

The video below shows 16 hours of neural development compressed into 40 seconds of a developing zebrafish's nervous system. Notice how the neurons branch to make connections with other neurons – a process vital to information transmission.

To obtain such accurate footage, the animal's embryo was suspended in water, rather than gel, and its photographers used gentle light sheet technology to capture the specimen in 3D, at a high temporal resolution.

...

Do animals see the same way we do? Do some animals have better vision than humans? The senses of animals have evolved to give members of the species an optimum chance for survival. Here are a few examples:

Some animals, such as cats, have a reflective surface ( tapetum) on the back of the eye behind the sensory receptors (left image above). When light first enters the eye, some light is detected by the sensory receptors. The light not detected by the sensory receptors continues onto the reflective surface at the back of the eye. This light is then reflected outward toward the sensory receptors, providing a second opportunity for detection. This feature produces two results. First, the outward reflection results in the shining of the cat's ey ...