is it coming in at the seam / stitch? When the bunk is new, the thread used to sew the canvas ends it's thin, to seal the hole the needle made, the thread needs to get wet a few times and it will swell up, sealing the hole. Sometimes it won't seal a particular hole for whatever reason. I have used a flexible, clear, uv/outdoor, temperature rated silicone to dab in the area that the water came in. This was done on the outside. If done carefully, you will never see the silicone. As long as the water is coming in through a needle/thread hole.
2014 Roo 21DK