Undersea World
Appearances: Worlds and mobile versions
Theme: Aquarium
Price: Worlds version:
20 trial passes
Mobile version:
$1.99 for unlimited access or 3 trial passes per visit
Hero: Captain Nemo
Difficulty (on a 1 - 5 scale, with 5 being the hardest): 2

"Hold your breath and dive in to a terrific Undersea World!"
- In-game description of Undersea World

Undersea World is a premium world in the Worlds and mobile version of Rail Rush.


Somewhere in the ocean, there is a huge secret aquarium that is home to giant sharks and the monstrous octopi best known as the Kraken. Who would be so outlandish enough to tame and keep such terrifying beasts, and for what purpose, is anyone's guess.

How to Unlock This WorldEdit

This is a premium world in the Worlds and mobile version, and is not available at the start.

In the Worlds version, this world can be unlocked if the player collects and pays twenty trial passes, which can only be obtained through many rock eggs.

In the mobile version, this world can only be unlocked through an in-app purchase of $1.99, but players can visit this world (without being able to unlock or use Captain Nemo) at the cost of three trial passes per visit.


There are three sections in this world:

  • Metal Tunnel: Any run in the Undersea World begins in a dark, metal tunnel, flooded with water.
  • Glass Tunnel: Sometimes, the tracks in a metal tunnel can lead out into a glass tunnel where one can catch a glimpse of the ocean outside.
  • Kraken Holding Bay: Sometimes, after exiting a metal tunnel, you may find yourself in a huge tank where tentacles are in the water. The Kraken is out to get you, so prepare for battle!


A full walkthrough video for this world can be found here. You may wish to turn on annotations, if possible, to see all hazards and sections.
This world is considerably easier than Amazonia World and Jurassic Jungle because side hazards will never appear in an alternating pattern, making them easier to anticipate and thus avoid.

All hazards below, except for the special hazard, can be found in either a metal tunnel or a glass tunnel. The special hazard is always found in the Kraken Holding Bay.

  • Upper Hazard - Portcullis: Sometimes, a portcullis (gate) with red flashing lights will lower over the central track to block the way. Quickly crouch to avoid hitting the spikes below it.
  • Lower Hazard - Fallen Rafters: Some of the metal rafters that support the tunnel\'s ceiling may collapse and fall onto the central track, posing as an obstacle that must be jumped over.
  • Side Hazard - Shark Tube: On the left or right tracks, a large shark may pop out from one of the tubes on the opposite wall. Lean away from the shark to avoid getting bitten.
  • Lane Hazard - Water Spigots: There may be portions of the course where three railroad tracks are available, but they will pass under a row of three large spigots (faucets). One or two of these spigots may open as the player approaches, causing water to violently cascade over (a) track(s), cutting it/them off. Just to make sure you know, the streams of water are dangerous on impact and must be avoided! This obstacle is best overcome by staying on the central track so that you only have to perform one hop if the central track is cut off. Staying on the side tracks can be dangerous because if your track and the central track get blocked by falling waters, you may not have enough time to make two hops to the other side, resulting in a fatal scalding. Sometimes, there may be a glitch in the collision detection that allows you to pass through the steam unharmed, but it is best not to count on it.
  • Special Hazard - Kraken Battle: Sometimes, instead of entering a glass tunnel from exiting a metal tunnel, you may head into a holding tank, where the music changes into an ominous tune! This means that there is a Kraken out to get you with its huge tentacles! Quickly hit the corresponding keys (Worlds version) or tap the indicated flashing red rings on the screen (mobile version) to fend off the Kraken's tentacles as they emerge from the water slowly, one at a time. In the Worlds version, if you hit a wrong key, the Kraken will instantly seize you and pull you into the water unless you have a Second Chance, so be very careful! Captain Nemo can hold off some of the Kraken's tentacle attacks with his electric harpoon. Kraken Battles are also known to be slower and easier than Snake Ambushes in Amazonia World.


  • Pairs of portcullises and fallen rafters are known to appear as the player progresses, and the way they appear may confuse the player into making the wrong move (such as crouching when he/she actually needs to jump). This is especially true when fallen rafters appear to resemble upper hazards at first until they crash down onto the track. Extra caution is advised in this world.
  • The exit door of every metal tunnel will have a picture of a crab, which is the logo of Silent Bay Studios, the company responsible for developing this game.