Just remember to expand your PTVs appropriately to account for rough seas.
You find this funny, but I have actually thought of a business plan for a big cruise ship full of LINACs sailing around the world, while all the passengers undergo treatment.
I would fill it up with breast and prostate cancer patients, but one could take on some more "fitter" patients onboard too, like postop sarcomas and so on.
H&N patients would be a no-go, since their presence alone would ruin the day for all the other passeng... I mean... patients!
The LINACs would be based in the lowest deck, so you don't need towards the bottom, making the ship lighter. One could actually install big fishing nets behind the ship, that would gather all the dead fish that would be irradiated to death when the gantry is pointed at 0° and killing all the fish that are swimming beneath the ship.
I would irradiate all of the day and offer cheaper prices for those, that opt to receive treatment during the night.
As a propulsion I was thinking of a nuclear reactor, so particles would be available for irradiation too.
I would sell the rights for TV shows to big networks, so that a soap opera could be produced aboard. That would be a good PR-boost.
I would have exclusive rights to sell medication onboard and passengers would not be allowed to bring their own medication. Therefore, through good deals with the pharmaceutical industry, big profits would emerge.
Just think of all the antiemetics patients would need!
So, what do you think?