一般现在时用swim，
现在进行时用swimming。
swim是一般现在时，表明了现在经常发生或者习惯性的行为。
例句：
I swim a mile a day.
我每天游一英里。
She's gone to swim.
她游泳去了。
I like to swim, especially in the sea.
我喜欢游泳，尤其喜欢在大海中游泳。
swimming 是进行时态。
例句：
We went swimming very early
我们很早就去游泳了。
If the tide was in they went swimming.
如果
涨潮了，他们就去游泳。
He drove through the gracious suburbs with the swimming pools and tennis courts.
他驾车穿过设有游泳池和
网球场的舒适城郊住宅区。