Kangaroo is going to put on a scuba mask and equipment to go underwater to explore, an awesome sea adventure that you take part in as well, as the title character.
The animal is going to run on the platform, and you have to hit the meter with the space bar at the right moment, meaning as high as possible, to take a deeper dive. As you drive down and then return up, if you encounter enemies, you are going to press the space bar in order to attack them with the harpoon.