All swimming is interval training.
Just being in the water is energy consuming. One must keep warm, and the resistance in the water makes all movements strenuous. You will receive guidance based on your technical skill level, and will be able to complete an adapted distance that corresponds to a good training session.
You can vary and train on different swimming types and in addition challenge yourself on elements of lifesaving, as well as diving and jumping.
Swimming electives take place in Elverum swimming hall which is 1500 meters from the school.
If you think your sport is hard, try doing it while holding your breath...