Squid (squirt) power

this was part of the early thought process behind the development of the water jet engine, (jet skis, etc.) if I recall. Unfortunately, this will not develop sufficient power for planing boats. But if you want silent, slow cruising in sufficiently deep water - not the normal 3 attributes for recreational boating, have at it

And what exactly is the advantage of a silent propulsion, other than allowing ballistic submarines not to be detected, and thus being able to start World War 3? Also, those marine life that have been able to survive because they could hear us coming now will be able to be killed.

re; Nelson
Boomers are a retaliation platform. An ICBM first strike will be carried out by ground based missiles. Keeping the boomers hidden helps keep the peace.
Years ago a whale was hit by a hydrofoil one of the noisiest boats imaginable. The postmortem on the whale showed that it was stone deaf on the critical frequencies from too much exposure to load noises. Also when you are surrounded by load noise makers all making similar noises Identifying the one that is closing in on you is difficult. In the long run quieter boats would be easier to hear.

Efficiency is much greater.

Imagine a sub built non-metalic using this silent running. It could smuggle merchandise undetected.

Whales and dolphins have been shown to suffer greatly from the noise of traditional prop systems. Silent or near silent ships will at least reduce this. Mind you I don't believe it is likely to be adopted commercially unless it can be demonstrated to be efficient as well.

Don Duncan, Shhhh!

hows this compare to estd waterjet propulsion now used?? See no difference save the Navy funding for Sub & ship use alone

For biomimetic propulsion, I would prefer fishtail technology. Just as quiet, just as safe for wildlife and theoretically can scale up to much faster speeds. After all, the sailfish can exceed 60 mph and a slew of other species would leave the fastest submarines in the dust.