swim为谓语动词，只能作句子谓语。swimming为非谓语动词，属于非谓语动词中的动名词，具有名词的特性，可以作句子主语、宾语、定语以及表语等。
swim
1、He can also swim. 他也会游泳。
2、He can swim. 他会游泳。
3、We could all row a boat and swim almost before we could walk. 我们所有人几乎在还不会走之前就已经会划船和游泳了。
4、All of the passengers started the day with a swim. 所有的乘客那天一开始就先游了个泳。
5、When the boat sank, they had to swim for it. 小船下沉的时候，他们不得不游水逃生。
swimming
1、Do you like to go swimming? 你喜欢去游泳吗？
2、Re-apply sunscreen every two hours, especially if you have been swimming. 每两个小时重新涂一次防晒油，尤其是在游泳的时候。
3、I went round to Jonathan's to see if he wanted to go swimming. 我去乔纳森那里看看他是否想去游泳。
4、Swimming is helpful for bones that are porous and weak. 游泳有助于改善骨质疏松和骨骼脆弱。
5、It was too chilly for swimming . 这时候游泳太冷了。