Shadow Wave's visual effect is visible to the enemy through the fog of war under the following conditions:

1. Enemies must have vision over the last known location of you
2. You must cast Shadow Wave on yourself

This way, a part of the visual effect draws at your last known location (a pink glow), and the heal beam is visible on your actual current location through the fog of war, pinpointing your position.

The video clearly shows how it basically reveals Dazzle through the fog.