Pickup 30 CREDITS which are both laying on the ground, then explode the set of doors in front of you to reveal a second tunnel. Note that the fireballs travel in the same direction in both tunnels.
Equip the FIRE EXTINGUISHER and wait for a fireball to pass before heading into the tunnel in the direction the fireball came from. Extinguish the flames to reveal more GEM STONES, before running back to the area you just came from so that you can allow another fireball to pass.
When it’s safe, again head left into the tunnel past where you just extinguished the flames and drop into the small pool of water. Hover below the surface as another fireball passes before climbing out and continuing in the same direction.
On the left of the tunnel, there is another explodable door on the left – this time the kind with the horizontal black and yellow stripe. Use the doorway as a refuge from the next fireball, but don’t bother exploding the doors as there are no items behind them.
After another fireball has passed, head left into the tunnel and again continue in the direction the fireballs are fired from. Hug the right wall until you come to a final set of explodable doors as you near the end of the tunnel.