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Super Mario 3D All-Stars

The Secret Undersea Cavern

Ben Chard
Jarrod Garripoli
, &
Seren Morgan-Roberts


This page offers a walkthrough of the level The Secret Undersea Cavern in Beach Bowl Galaxy.

Smash the Rock Wall

Hop on into the water and find a green shell. There are several dotted around the ocean floor. There are also a few chests around that you could throw shells into to earn a few different rewards, like 1-up mushrooms and star bits. Once you’re ready, throw a shell into the cracked wall that’s directly behind the penguin. It will reveal an entrance into the secret cavern.

Secret Cavern

When you enter the secret cavern, you’ll find lots of wooden crates. They’re filled with various things, including star bits and a Goomba. At the end of the cavern is a big fence. There are some crates you can break open to reveal a hole through the fence. Within, you’ll find a tree stump. Groundpound it to reveal the Star Launcher.

Smash the wall using a shell to reveal a secret cavern.

Tox Boxes and Thwomps

This next area is a little tricky as there is a new enemy: the Tox Box. They look a little like Thwomps except they roll around a path, fatally squashing you if you’re in their way. The only way to avoid them is to stand on a tile when they land with their mouth open. This will protect you and you can get behind them on their path.

After your first Thwomp and Tox Box, you’ll come to a section with multiple rotating platforms that are elevated above a waterjet. If you drop into the waterjet you’ll be transported straight into a blackhole and have to begin the section again - including the tedious Tox Box and Thwomp! The best way to navigate this tricky section is to walk upwards with the rotating platform and then jump onto the next clear platforms, whilst avoiding the concrete blocks that’ll push you off the platforms. When you’ve made it across you’ll come to a stoney bridge that’ll take you up along a stone path.

(1 of 2) Hide in the Tox Box’s mouth so he doesn’t squash you

Hide in the Tox Box’s mouth so he doesn’t squash you (left), and make sure you avoid the Thwomps too! (right)

On this stone path are a few more Thwomps and Tox Boxes, just make sure you’re not on their tiles when they smash into the ground and you’ll be fine. There are a few 1-up mushrooms on the path. If you’re having a hard time getting past the Tox Boxes, you might want to spend the time trying to get the 1-ups to prevent a game over.

Break the Crystal

At the end of the path of Tox Boxes and Thwomps, you’ll find a big Crystal with a Power Star trapped inside. Spin attack to break the crystal and grab the Power Star to end the level.

After a difficult journey, you’ve reached the Power Star!

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Guide Information
  • Publisher
  • Platforms,
  • Genre
    Action Adventure, Platformer
  • Guide Release
    24 September 2020
  • Last Updated
    8 February 2021
    Version History
  • Guide Author
    Seren Morgan-Roberts, Jarrod Garripoli, Ben Chard

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This guide for Super Mario 3D All-Stars offers a walkthrough for all three Mario classics.

Inside this guide you will find:

A 100% Walkthrough - For Super Mario 64, Super Mario Sunshine and Super Mario Galaxy.

A complete guide on Super Mario 64, including:

  • A layout of Peach’s Castle, with each course’s location pinpointed, as well as an overview of each course.
  • Walkthroughs for every star, including all courses’ 100-coin star.
  • How to get each of the power-up caps.
  • The location of every single Secret Star found in Peach’s Castle.

A complete guide on Super Mario Galaxy, including:

  • A Dome Overviews page outlining every galaxy found in each Dome.
  • Walkthroughs for every star, including hidden stars and comet stars, found in each galaxy.
  • A guide on how to unlock the Planet of the Trials galaxies.
  • Detailed coin-by-coin walkthroughs of Purple Coin levels.

A complete guide on Super Mario Sunshine, including:

  • Walkthroughs for every shine in every episode.
  • How to find every Blue Coin.
  • Strategies on how to secure 100 Coins on every Course.

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