World 4-Water World
Many of the levels in World 4 take place underwater, which makes it hard for Mario to pass by obstacles and enemies with any agility. Underwater, Mario can’t use his head-pouncing abilities, so power-ups like the Fire Flower, the Ice Flower, and the Penguin Suit are extremely valuable.
In fact, the Penguin Suit makes Mario a very agile swimmer! Luckily, many enemies in the water don’t actively pursue you, so you can avoid them if you’re patient.
