Shellac is not water sensitive. It is sensitive to prolonged alcohol contact which is it's solvent.

Here's a pulling boat I built with uninspiring wood color and a detail stripe of flame maple.

I masked off the area surrounding the stripe and used shellac to seal the wood of the detail stripe. Make sure tape edges are firmly pressed into the wood to reduce bleed through. Then seal with a coat of clear shellac. Then mask the stripe and sand any shellac bleed through. Dye the wood edge BELOW the stripe using gravity to reduce any bleeding of the dye into the stripe. Do the same for the other edge/side of the stripe.

Then mask around the stripe again and lightly sand away any bleed through of the dye off the stripe edges.

The contrasting stem is an applied veneer with hardwood above the deck.
I used copper tape for detail stripes on the deck below.