Do I risk ripping up some delicate rubber with the drain snake?
Yes, you do.
Well, not REAL delicate, but you'll want to be gentle. If you crawl over the queen bed and remove the back panel you will see what you're dealing with - a ribbed (not for your pleasure) tube that is also attached with a "T" to the sink drain.
You can back flush it with a blast from the garden hose from the transom drain back into the transom well if you thoroughly plug the sink drain first.
I made a removable-for-cleaning screen to prevent this from clogging, as have others on this forum. After you've cleared it out, you can make one for yourself by coiling a small square of window screening into a cylinder and sticking it into the hole to make a screen-type standpipe. Fastest, cheapest functional, time-saving mod you'll ever do.
Note that a puncture at a low point in the hose has the potential to completely swamp the boat,

especially if the transom drain is at, or very near, or below

, the water line on your boat.
