On the first SOF I built I used a transparent deck "sealer" - an Olympic product, IIRC - to help protect the plywood frames. I used the red-tinted version, and it did lend a red color to the frame, but the solid pine absorbed the least amount while the WRC took on the most color. In the photo below, the uncoated piece of WRC perpendicular to the coated WRC floor slats helps illustrate the degree of color change. The frame is several years old now (and some of it has been pirated for use in new kayaks) but the finish still seems to keep water from being readily absorbed into the wood. The product that I used was solvent-based and it did strip the wax from the lashings, although this did not seem to create any problems; just something to be aware of...

: Good idea! That is why I ask! I wouldn't have thought of that. To
: hung up on furniture type stains.