The first water level event the player touches should ALWAYS have Instant set to 1. After that, you can have it instant or non instant, but until you've touched an instant, non instant water levels will not work.

For water level, the water's top is the Y pos that you set. If set to 0, the water level will be wherever you are when you touched the event.

If the water level is higher then about 128, instead of swimming, you will walk around in the water. It will behave like normal non-water, except with incredibly low gravity, and toaster won't work.