Keep in mind that most ship pools are salt water, not fresh (its pumped in from the ocean). Plus its not always very warm. Theres also the "pee factor" that might be in there, and if your child isnt potty trained they wont let her in the water.
A nine month old is pretty big for this, but it might work. I have a solarveil sling (a simple mesh one would work too) that can get wet and dries quickly. You could put the child into the sling and bathe her in it. Little ones are really slippery and this helps a lot. Plus they will feel secure next to you. I do like the inflatable bath tub idea though. Be sure its small enough to fit in those tiny showers, and leave room for you to get to the child!