Annette Lake is my favourite paddle in Jasper. Located just north of Lac Beauvert and south of Edith Lake, it takes about 45 minutes to paddle around the lake.
The colour of the water is spectacular on a sunny day and the beach is a nice diversion for cranky kids.
The small size of the lake mean that it is often glassy calm and you can see the undulating bottom. You'll often find scuba divers in the NW corner of the lake.
The easiest place to put in is off the main beach. There are three parking lots and you want the right-most one when you come into the park. This requires about a 40-foot carry to the water. There is also a picnic area here with washrooms visible across the field.
The beach is quite lovely and can be busy on a nice day. The brave can even swim in the lake. I've only been in once (one day when it was 34 degrees outside) and it was a good break. The water is quite shallow so you can wade out quite a ways.
Annette is very picturesque due to the colour of the lake. Here a shot (alas, not mine) of Annette on a stormy day. There is a paved path around the lake (about 2.5km) that is wheelchair accessible.
A nice day is a morning paddling at Edith Lake, lunch and the afternoon on the beach at Annette, dinner at the Jasper Park Lodge and an evening paddle on Lake Beauvert.