I have to relate this story of our 3 year old, 6 lbs yorkie. This summer we had planned a 2 week trip to the Channel Islands off the California Coast. They do not allow any pets landing on the Island. Before heading out, I had tried to obtain astroturf from the Home Depot but it was a special order and I would have to buy much more than I needed (plus it would arrive after our departure). We sail out of San Diego by the way. I bought a piece of grass sod from Home Depot for $3 and took our dog to it in our back yard regularly for a week. I learned that he likes a "fresh" area to do his thing so as time went on he would not want to use the sod. We even took the sod to the boat to let him try it out. What a mess from all the mud. I nixed the idea. After some research we mail ordered a UGODOG potty tray & took off on our trip. We lined the bottom of the tray with a pad impregnated with some kind of smell. Did not work. So here we are, anchored at a cove trying to convince our dog to use this tray which is out on the foredeck, when my 14 year old son says something like... "if we can't take the dog to the shore, maybe we should bring the shore to the dog." I went to the shore in the dinghy with an empty coffee container and returned with it full of dirt, pebbles and sand. I spread it out under the grate, and on top of the pad, replaced the grate and viola. Sure there were a few misses, but over all the dog used the UGODOG regularly 3 times a day. We would leash the dog and walk him out to the foredeck just like we would take him out at home. The smell of the dirt under the grate was the attractant.
Now I can continue to plan my cruising life 4 years from now.