I imagine it'd be easier to build an indoor simulated lawn then trying to do that on a ship. And, well before the point where a gigantic ocean liner becomes ec

I imagine it'd be easier to build an indoor simulated lawn then trying to do that on a ship. And, well before the point where a gigantic ocean liner becomes economical - you could always get a custom set of lawn darts crafted for you by any sort of metal working shop or factory. Heck, you can probably get them on Etsy from China.