Hello! My shower drain would not drain. As you say accessing the hose under the shower pan is very difficult. I ended up using an air compressor and was able to blast the existing hose mostly clean using air. Had that not worked, my plan was to disconnect the hose under the shower pan, most likely requiring cutting an access hole in the pan (or, if lucky I might have been able to reach the undershower end of the hose by taking out the house battereis that reside under the settee, however there there is a rib under there on my boat that would most likley be in the way.) Then disconnect the other end of the hose where accessible in the bilge and attach a new hose to old hose and pull it through. Then repair the shower pan. Perhaps someone has come up with a better solution. I hope so!