Swimming is always a good idea to spend your time. This activity requires the work of all parts of the body, increases efficiency, improves coordination and gives a lot of pleasure.
Even better idea is to going to the pool with your boyfriend or your girlfriend. Seek an object which is open at night. At the evening, it shouldn't be a lot of people at the pool so you'll have plenty of space for yourself.
If it's the right time of the year and the temperature is appropiate, you can swim out.
The view of your partner's wet body in the moonlight, the soft rustle of water interrupting the silence... the perfect date. Especially for romantics.
Alternatively, perhaps even more interesting option would be swimming in a lake, not in the pool. But in this case we should know well the lake and take care of security. If it is not possible, choose a pool.