Matilda's Own Chacopa erasable yellow fabric pen.
This pen is technically not water-erasable but has a key benefit - you decide when to remove the marks! It comes with its own eraser - only use the eraser to remove marks, using water may cause the ink to spread.
This pen can be used on light denim to mark out patterns to stitch (see product photo).
NOTE: For best results test marking pens on an inconspicuous part of your garment first (e.g. an inside seam), as they can be difficult to remove from certain fabrics. Remove any marks before you iron, as heat could set them permanently.
Made in Japan.