First you go through the door and there is a cave go inside it.You will get after the blue dragon tells a power then go out of the cave and go near gadget of professor with 8 light gems then complete the gadgets task and you will go to a new world.
Crocovile Swamp- In one of the passageways, there is a brick that is a different colour (blue) from the rest. Charge it and you will get a Light Gem and gems.
Costal Remains- In on of the beaches, destroy all the dark gems. A large coloured thing will arise from the water. Keep going up the pillars onto it. Head-bash the centre. You will find a Light Gem and the portal to Sunken Ruins.
Also in Costal Remains: Once you get the AQUA BREATH, use it on the wheel in one of the beaches. A platform will go up, and youll get the Light Gem in the air.