When you are working on a series of training cycles – which may be 4 to 6 weeks long – you should insert a rest week at the end of each cycle.
A rest week could be 3 to 7 days long.
A rest week allows more substantial rest and recovery for the performance systems that have been working specifically in your intense swim training. During this time you should continue swimming in some form as long as the level of stress and energy expense stays low. You may enjoy other athletic activities, as long as they do not drain you of the energy that needs to be restored nor put strain on the systems that are recovering.
Also, be aware of activities that are enjoyable. Swim in the ways that are most pleasant (without strain).
If you want this decision really simplified you may consider repeating the practices from the previous week, but cut the distance (repeat and total distance) by half, and lower the effort level. Certain practice sets may already have low physical intensity while others may be more demanding, therefore use your discretion about which kind of sets are suitable for allowing your body to get some stimulation which still allowing you to rest.
If you are doing the right kind of rest you should notice both your energy and your motivation to swim getting stronger. If it is staying low, even after a week, check in with your coach and consider you may need more rest, or a deeper form of rest.