Instructions
Climb the hill. Use a combination of Mario's wall jump and FLUDD, the water-fueled jet pack, to get to the top of the hill where the three mirrors sit.
Stand on the opposite side of the first mirror from the enemy. The first mirror features one enemy.
Spray the enemy with your water to push it closer towards the edge.
Ground pound to flip the enemy off the mirror.
Repeat this process for the other two mirrors. Mirror two pits Mario against two enemies, while mirror three has three enemies.
Collect the shine, which is at the end of the beach.