OctoShoals
First thing you should know is that, despite being underwater, all your bombs will work here unlike at Lake Mensor.
If you have him, equip Marine Eel, as the Homing Ability is a big plus here. Be careful if seaweed blocks your way through a passage. They can grab you for two small hearts damage. You can either stun them with a blast or send a bomb at them to briefly distract them. Be careful of squid-like creatures with two tentacles or ones that look like little gray ghosts. Both of these go out with big bangs, so be sure to hit them from a distance. Not too far in, you'll run into a Charabom Battle portal for Kai-man, a level 4 water-type. Any Charabom you have should handle him easily, allowing you to use his Shield ability to help reduce damage in dangerous situations...such as just ahead where two seaweeds in quick succession block the way. Rather than take a chance in trying to stun both of them at once, you can use Kai-man, distract the first one and let the other grab you. The Shield will mean you only take one small heart of damage, and you can quickly run through afterward.
Now you'll encounter the bubblers. When Bomberman hits one, he'll float up and down on them. Move the control stick forward to make him progress. If you time the press so that he's at the top of his float, he'll make a floating hop. Try to see if you can hop from bubbler to bubbler. This will help you later when you have to avoid spike fields. Soon fish enter the equation. They'll interfere with any hops you try to make, so time your moves to not only hop at the top of your bounces but also when the fish are low and not in your way.
After riding up a bubbler to a ledge and crossing a bridge full of exploding creatures, you'll come across hermit crabs. Throwing or kicking bombs will normally cause them to hole up in their shells to block the blast, so try Homing bombs from Marine Eel. Now look at the waterwheel with the red switch (for future reference, all red switches must be blasted to activate). Blasting the red switch will cause the waterwheel to reverse direction temporarily. You can ride the waterwheel when it's reversed like this to proceed forward. The switch to the second one is across the gap, so switch to Andlar and throw a bomb so that it can blast the switch. Turn left from here to find two more waterwheels in quick succession. Use Andlar again to quickly plant a bomb and then throw a bomb so as to trip the two switches in quick succession, allowing you to navigate both of them before they switch back.
Past the exploding creature near the bridge and the two seaweed is a house that constantly streams out lots of fish, preventing you from going anywhere with the bubblers. Throw a bomb onto the red switch. When it goes off, the house should briefly stop releasing fish, allowing you to get across to the ledges and reach the final spike field. Navigate this final obstacle and the exit will be just ahead (rest easy; there is no miniboss in this stage).
Lightning Cards
- Past a spike field with three bubblers and before the first field with fish is a ledge and a boulder. Take out the exploding creature on the ledge, then use a bomb on the boulder to uncover a bubbler (luring the creature near the boulder might let you do two jobs with one bomb). Ride the bubbler to the ledge and the Lightning Card.
- You need a Bomb Jump Charabom. Past the second waterwheel, take the right path and Bomb Jump your way across the gaps (use a Big Bomb on the second one) to reach the Lightning Card.
- You need Light Bombs. On the ground to the right of the ledge where Card #2 is kept is a translucent box. It has the Lightning Card inside, but you need to make it solid first with a Light Bomb.