in the water, swimming in the water
如果要表达水里有某物品,应该用in. 如果要表达把某物品放进水里,则用 into.
比如:
There are some stones in the wate. 水里有一些石头。
Please put these stones into the wate. 请把这些石头放进水里。
因为游泳本身就是在水里的,就不用加“在水里了”: She is swimming. 如果说 She is swimming in the wate, 就有点怪了。