13. Even though he couldn't swim, he will have a try.
尽管他不会游泳，但他要尝试一下。
还能这样说：
He will try to swim even though he couldn't do it.
He would like to take a crack at swimming, even though he couldn't do it.
应用解析：
try on 试穿；
try it on 做大胆的尝试来考验别人是否能接受；
try one's damnedest 尽自己最大的努力；
try one's hand at sth. 初试身手
14. Swimming is good for health.
游泳有益于身体健康。
还能这样说：
Swimming is healthy for body.
Swimming contributes to good health.
应用解析：
the health of body and mind 身心的健康；
be out of health 身体状况不好；
public health 公共卫生；
to your health 祝你身体健康
15. We will have a swimming test every summer.
我们每年夏天都会进行游泳考试。
还能这样说：
We are faced with a swimming test every summer.
A swimming test will be held every summer.
谚语：
The best fish swim near the bottom.
好鱼常在水底游。
16. I choose swimming class as my optional subject.
我把游泳课作为我的选修课。
还能这样说：
Swimming lesson is my elective course.
I choose swimming lesson as my elective course.
应用解析：
optional course 选修课，选修课程；
optional equipment 附加设备；任选设备；
optional item 可选项目；
optional route 可选路线；
optional service 可选择受理的业务
17. We applied for a membership card in the natatorium.
我们在这家游泳馆办理了会员卡。
还能这样说：
We became a member of the natatorium.
We could swim in the natatorium with our membership card.
应用解析：
apply oneself to sth. 专心致志于某事；
apply sth. to sth. 运用、应用某事；
apply to sb. 适用于某人