The thing I like about ground-effect over-sea vehicles is that, unlike hydrofoils, they're not majorly reliant on very fast blades chopping through whatever comes across their path in the topmost layer of the ocean, where life tends to dwell.
As a species, we really need to start considering our maritime-based cousins a bit better. The last few decades have been hellish for them, noise and all.
It depends on your requirements. This is the description from the Nemesis, a cost-is-no-concern ultra-yatch:
> The NEMESIS ONE will be the World’s Fastest Luxury Foiling Sailing Yacht, able to break the 50 knots speed barrier, while flying on computer controlled hydrofoils. [1]
So a breakthrough fantasy hydrofoil is trying to reach 50 knots. I suspect that, looking at significant figures & complexity of build, for anyone wanting to be able to get to 75 knots (88 mph) there'd be nearly no one justifying hydrofoils. Even at a reduced speed like 45 knots, I suspect the control problems & additional drag of running a foil start to be pretty unruly & inefficient, and that wing-in-ground very quickly gains appeal for simplicity & efficiency both.
Once we start thinking about wing-in-ground, with denser air, it makes even more sense to start looking at ideas we explored earlier in aviation, like lifting bodies, where we can reap yet more efficiency.
The best counter-example to myself I can come up with is the VT Halter Marine Mk Mod 2 High Speed Assault Craft[2], specs unknown. But I tend to think of hydrofoils as more like the 180t Sea Slice[3], powered by two 3840 hp diesel engines, capable of 30 knots. My eyes & intuition all tells me flying is more effective at speed, and that we have a lot of efficiency we could be gaining from wing-in-ground/sea.
As a species, we really need to start considering our maritime-based cousins a bit better. The last few decades have been hellish for them, noise and all.