求教一个英语问题

我同意你选unless，因为unless本身就带有if...not的意思，也就是说if the water is too cold,I don't like to go swimming.如果用if我到觉得根本不通。

unless 作连词：
1.used to say that something can only happen or be true in a particular situation 除非；除非在…情况下
You won't get paid for time off unless you have a doctor's note. 除非你有医生证明，否则你不上班便拿不到工资。
I won't tell them—not unless you say I can. 我绝不告诉他们 除非你允许。
Unless I'm mistaken, she was back at work yesterday. 除非是我记错了；她是昨天回来上班的。
He hasn't got any hobbies—unless you call watching TV a hobby. 他没有什么爱好 除非你把看电视也称作爱好。

2.used to give the only situation in which something will not happen or be true 若非；如果不