Fresh water tank or the water heater tank?
I have to admit, I've never even seen a Shadow Cruiser 5th, so, I'll have to go with generalities
That trailer is getting on 20 years old, so, the odds of finding somebody on here with one is going to be slim...
Fresh water tank should definitely have a hose accessible underneath and visible from the outside. Many have a rotating 90 degree valve, others, may just have a plastic pipe with a screw on cap... It may be hard to see...IIRC, the one on my 210WBS required me to crawl under the trailer, look up at the bottom of the fresh water tank and almost in the middle of the tank, on the edge, was a short pipe (~2" long) with a 90 degree petcock valve. Just glancing under the trailer, you'd never see it. Other trailers, it is easier to find...looks like the low point drain pipes, but, located by itself and only one pipe. Again, it may have a 90 degree petcock valve or just a cap (as my Cougar has).
Water heater? No drain valves...just pull the anode and let'er rip!