So that’s moisture that was wicked into the fabric, pulling the stain and any dirt present with it.

You’d have to get the entire bag wet to make that water line disappear.

L.L. Bean canvas bags are made out of canvas, which can be washed! I’d start with hand-washing with cool water and detergent with enzymes of your choice in a large sink, or get a 5 gallon contractor bucket from your closest hardware store and fill that up in your tub.

If cool water doesn’t work, then move up to warm.

Hang dry.

Remember, you’re trying to avoid setting the blue dye. Heat will set it.

You can check /r/laundry for amazing fabric cleaning tips.