because the water should not open our mouth
it is made of... material soft smooth material.
It's soft, low-impact with a smooth resistance.
Obviously the pool floor is not smooth.
it has a smooth skin body so nothing gets caught when swimming
Oh honey, a lake filled with people boating and swimming won't act like a mirror. Mirrors reflect light perfectly because they have a smooth surface, while a lake is all rippled and wavy from those rowdy swimmers and boaters. So unless you're looking for a funhouse mirror effect, I suggest finding a real mirror for your reflection needs.
We went swimming in the sea. The sea was calm/smooth/choppy/rough when we crossed the Channel.
No, 'swim' is not an adverb. It is a verb because it is something you do, whereas an adverb is used to describe an action. An adverb form is "swimmingly" but it does not directly relate to swim or swimming. It means in a smooth or easy manner.
so the animal can slide out when it gets to big
Having wet, saturated skin just increases the risk of your slipping. It's a danger hazard.
Frogs have a streamlined body shape that is adapted for swimming and jumping. They have long hind legs for leaping and short front legs for stability on land. Frogs also have a wide head, bulging eyes, and a wide mouth for catching prey.
I have personally never heard of "stains" for coloring swimming pools. you can however have your pool resurfaced. there are many different options to do so. My personal favorite is called "diamond brite". it is a prety smooth surface, and is availablr in many different colors!
Probably some thing like soft, smooth or somthing or up beat.