Even on our boat with a water heater, we find that we use the solar shower more often. We hang it on top of the cabin and run the hose in through the window in the head - works great! We've used the garden sprayer (also works good, but the spray is a bit "thin") and the Zodi (especially good when it's cooler out and you have no other means to heat your water... recirculate the water into itself while heating and it heats up much faster... turn off the propane when you have the water hot enough and it works good for as long as the water lasts... we frequently used it for washing dishes on our tri). The garden sprayer also works good for cleaning off the deck of the boat (at the time, we had our tri in a marina that didn't have water at the slips).
You can make anything work. However, when it's easy (and toting water is rarely fun) you can stay out longer. That's why we opted for the water heater when we're plugged in (and it will keep the water hot for most of the day), and solar shower on Wild Blue when we aren't plugged in. For those who think the head is overkill in a 25' boat, it's nice to have a private place to shower. If you can't close off your cockpit with canvas, you can get one of those camp shower enclosures. On the other hand, if you're so close to neighbors that you might scare them when you shower, you are likely pretty close to shower facilities onshore. YMMV.
Best wishes,
Jim B.