In some episodes they make a 火, 消防 but how do they possibly do it underwater?

Welcome to the mysterious world of cartoon magic.

A 螃蟹 with a 鲸, 鲸鱼 as a daughter??

哈哈 the creators were probably high. XD

Easy, they go against the impossible. Such as Sandy, what 松鼠 lives underwater with an astronaut suit. Also who lives in a Pinapple with a pet 蜗牛 that meows like a cat? No one except Spongebob(:

itscalled imagination!

How to make 火, 消防 underwater in 3 simple and easy steps
Step 1: Physically be in a cartoon
Step 2: 你 most likely could not do step 1
Step 3: Realize that steps 1 and 2 are not simple and easy
Step 4: Now realize that there's 更多 than 3 steps
Step 422: And now realize that steps 5-421 were completely skipped. Also that there's way 更多 than 3 steps...

ITS ALL IN THE WORK OF BRAINS!

Water proof matches! (LOL!) :D

Because it is a cartoon