Shark Tunnel

A Stock Video Game Setting consisting of an underwater tunnel with glass walls. Expect to see all sorts of fish and aquatic life on the other side of the glass. Actual sharks are common, but not required.

These are especially common in Racing Games as a Justified Under the Sea race course.

Compare Under the Sea and Down the Drain.

These actually exist, as Wikipedia can attest.

Examples of Shark Tunnel include:

Film

Jaws 3D has an underwater tunnel that gets attacked by the shark.

Literature

Animorphs 15: The team end up in one of these while trying to acquire sharks for their next mission. Ax assumes it's just an enormous screen, and is surprised to learn that they're actually surrounded by sharks with only "poorly-made human plastic" protecting them. When they get caught by a Controller, Marco asks Ax "Just how poorly made is human plastic?" and Ax smashes the glass with his tail-blade.

Live-Action TV

In the "Unfinished Business" season of The Amazing Race, there's a Roadblock where one member of each team has to dive into a tank of this type in order to find their clue.

Video Games

In Star Wars Episode 1 Racer, The Aquilaris track has these linking the various floating cities.
In F-Zero GX, Big Blue has these appear, with a giant fish visible.
Stunt Race FX: Even with the blocky early polygonal graphics, two out of three of the water-themed tracks had these, with sharks and sunken ships visible.
Extreme-G 2. Its not surprising that another futuristic racing game has a Shark Tunnel in it.
Final Fantasy VII has the pathway to the underwater reactor at Junon.
Earthworm Jim: While its name suggests a Down the Drain level, the Down The Tubes level is very much a Shark Tunnel.
In Super Metroid, Brinstar has a section where it crosses over Maridia, where a short Shark Tunnel separates them. A well placed Power Bomb shatters the glass, allowing free travel between the two.
Mario Kart Wii's Koopa Cape track, which was then averted when it reappeared in its successor to fit its new underwater-driving gimmick.
It makes an appearance in Onimusha 2 and 3. In the former, if you stand still near the glass and absorb souls for a while, a large shark will appear and chomp a school of smaller fish, giving you yellow souls.
In the first level of Gimmick!
Pulseman: The Australia level of Pulseman had a part like this.
Megarace: The Maeva tracks take place mostly in underwater glass tunnels.
Half Life: Opposing Force has these in the "Crush Depth" level.
World of Warcraft has one of these, albeit as a mode of transportation and not an actual combat zone, called the Deeprun Tram.
Sonic Colors: In the Wii version, Sonic goes through such a tunnel at the very beginning of Aquarium Park Act 1. This is because Aquarium Park is set underneath a series of massive interconnected undersea geodesic domes. Sonic arrived from the surface of the water. The DS version does not have such a thing, immediately starting Sonic underneath the domes.
Need for Speed III has an underwater Shark Tunnel in one track.
Crash Bandicoot: Roo's Tubes from Crash Team Racing; Deep Sea Driving from Crash Nitro Kart
Jaws Unleashed: A rare Inversion, where the protagonist is on the outside of the tunnel.
BioShock (series) has a lot of these tunnels linking the habitats of Rapture, with one tunnel featured early-on in an impressive set-piece where a wrecked plane crashes into the tunnel and starts flooding it.
Cruisn USA, and its Spiritual Successor, California Speed, both have a track with this.
The Beginner course in Scud Race / Sega Super GT has two of these, the first of which is called the "Dolphin Tunnel".
At least one level of Jedi Knight: Mysteries of The Sith features one, only with Drugons. Oh, and you are in the pool with them and must find your way inside in order to proceed.
Sonic and Sega All-Stars Racing has one in the "Ocean Ruin" track. It even has a loop-de-loop!
Medievil has The Lake, in which you walk through a tunnel of water, magically frozen in place by crystals. Outside are huge, blue elephant fish, which constantly trumpet as they swim around.
Wipeout Pulse's Vostok Reef.

Western Animation

The underwater train stations in Dinosaur Train.

Real Life

Truth in Television: The original Shark Tunnel is the one at the Shark Encounter exhibit, at Sea World of Florida, Orlando.
Atlantis resort in Bermuda has a waterslide that goes through a shark tunnel.
The Georgia Aquarium in Atlanta has a huge tank with one of these through it; the tank includes several huge rays and sharks, including one of the world's only captive whale-sharks. It's...kinda creepy when it passes overhead.
Deep Sea World in North Queensferry, Scotland, has one of the world's longest. The tank is mostly home to species found around the coast of Scotland, but also includes a collection of sand tiger sharks, presumably largely for the coolness factor.