What can't you do out of the water?? Well, I guess you are limited living in a cold wet flat country! The hockey specific stuff is pretty difficult but there's plenty of other training to get your fitness and speed up to scratch so that when you do get into a pool you've got something to start with.

I personally hate swimming so am always looking at doing what I can out of water. As with swimming though you should plan what you are going to do and what you want to get out of it. Sure swimming a straight 5km will help to some degree, swimming a planned 3.5km of sets, if done properly, will benefit you more.

Here's a couple of ideas:

Running would have to be the easiest as you can start exercising as soon as you get out the door. You can use running to increase speed as well as endurance. Fartlek training (see http://en.wikipedia.org/wiki/Fartlek) is a pretty good way to train. This method can also be applied to swimming or cycling too. Doing intervals using lamp posts as markers also works (also works with cycling).

Cycling is good for leg strength and fitness but you need to be doing some swimming at the same time as cycling can develop your leg muscles in the wrong way if that's all you're doing which can be detrimental to hockey/swimming.

Circuit training or boxing is great for high intensity aerobic work outs. You can also alternate circuit classes to do strength training (slower reps/heavier weights) one session, then speed (lighter weights/faster higher reps) the next.

Weights and stretching is also benefitial for hockey. Do overall body workouts but also think about all the muscles you use during hockey and work on them in a way specific for hockey (ie ankles, wrists, sholders, etc).

I also add some varitey with a few games of squash a week plus surfing and spearfishing, however I'm sure the weather's not that great for surfing in Holland!