The course and the second Bowser battle can be reached as early as after collection 30 stars.
Bowser In The Fire Sea starts out as a path leading over a lake made up of lava (or a "fire sea", if roughly translated from the original, Japanese wording).
Once the player has finished the main course and accessed a pipe, they will encounter Bowser for the second time.
In Bowser In The Fire Sea, Bowser is fought in an arena floating in mid-air over the titular fire sea.
Just like in the first Bowser battle, Bowser needs to be flung into the bombs surrounding the arena. Once Mario has flung Bowser into the bombs enough times, Bowser will be defeated and Mario will be able to access the upper floor of Peach's Castle.
If Bowser is thrown past the bombs and ends up in the lava, he will simply jump back up and land on the arena, shaking it and making Mario fall off it, if the player doesn't run upwards against the angled platform.
Falling into the lava is most likely certain death, if Mario can't get back up fast enough, as it will make him lose 2 slices of his health bar with each time he makes contact with it.
Screenshots (Bowser In The Fire Sea Course) Edit
- The Bowser in the Fire Sea course is notable as the only Bowser level, that features a non-generic name in the internal files. Internally, it is named "Bowser's Fire Sea", while the others are called "Bowser 1 Course" and "Bowser 3 Course".
- All Bowser boss battle arenas have generic internal file names and are called "Bowser 1 Battle", "Bowser 2 Battle" and "Bowser 3 Battle".