Swimming is a great alternative to running or riding the bike in your off season training. Some would say that it is much more effective then either because you use your entire body and a lot more energy. Swimming gives your whole body muscle toning while also offering terrific cardio training. The greatest thing about swimming in the off season is that you will not do as much damage to your joints as you would running or riding the bike. It is virtually stress free on your joints that are so often used in hockey. While in the pool still train the same way you would run, by doing either sprints or interval training.
When you sustain a lower body injury which is very common (I have a broken ankle right now) swimming is almost the only cardio training you can use. By going to the pool you can still do interval training and sprint training, sure it won’t be the same as sprints for your muscles but it will still have the same effect on your conditioning.
Start slow when you first get in the pool and build your way up to longer and longer swims, just like anything your body has to adjust to the new type of training.