This can be done in Chapter 1.
The seachantresses are found at the following places, you must land at each location for them to count towards the achievement:
- Redmouth Forge, southwest of the center point of the map
- Sacred Steps, near the northern edge of map, close to the centerline
- Witchrock, near the eastern edge of the map, slightly south of the Maw line
There is a Dunkle side mission titled "Seachantress Festival" that leads you to Witchrock if you want to get that one out of the way first. You will not be able to buy any chants from this location until you have visited the other two and bought their permits.
Here are pictures of the locations on the map.
Redmouth Forge:
Sacred Steps:
Witchrock: