Oh yeah sorry, I mistook which thread this was in. I thought you were proposing an alternative to high speed rail for Brisbane-Sydney-Melbourne trips. For a Redcliffe to Brisbane trip it might be a bit more viable, but the choke-point getting into the river past Fisherman Island might be an obstacle, and I think the speed limit in the river itself would be prohibitive to the boat being competitive with the existing train.

As for the sunny coast, there are already plans to add a rail link directly to the coast, and I think the problems with Redcliffe would be amplified on this route, thanks to the additional need to extend the trip to go around Bribie Island.

But I do love the out-of-the-box thinking.