It could be possible for a couple routes where launch and final approaches could be done over water. It'd need some shallow seas, so platforms could be anchored to the bottom, as well as some high-speed rail and some veeeeery long rail bridges connecting the spaceport to land.
A quick look at ocean depth maps points to friendly continental platforms around the East US, China, a lot of Australia and New Zealand, and most of South America.
It'd be a massive effort, but not completely impossible. To get to Brazil to see my family, I'd probably need to first go to Southwest Ireland before boarding a suborbital flight to Rio, so it'd be 2 hours of rail, then 20 or so minutes of suborbital, then another hour flying to São Paulo (which is not on the coast). Still beats flying through Lisbon, Amsterdam or Paris.
A quick look at ocean depth maps points to friendly continental platforms around the East US, China, a lot of Australia and New Zealand, and most of South America.
It'd be a massive effort, but not completely impossible. To get to Brazil to see my family, I'd probably need to first go to Southwest Ireland before boarding a suborbital flight to Rio, so it'd be 2 hours of rail, then 20 or so minutes of suborbital, then another hour flying to São Paulo (which is not on the coast). Still beats flying through Lisbon, Amsterdam or Paris.