>>11891630I asked this question once and basically the answer is people don't know yet. Salam and Strathdee originally proposed that black holes can be considered a form of gravitational soliton, which is a nice idea and seems to work. But we don't know about gravitational rogue waves.
The connection between water and radiation is basically just due to the somewhat interesting parallels between hydrodynamics and certain regimes of radiation.
You can't necessarily conclude that this does imply that gravitational rogue waves also exist, since the sine-Gordon equation has soliton solutions but does not have rogue wave solutions, to give one counterexamples.
Almost all rogue wave research right now is also extremely low quality and some outright bad. It's very underdeveloped as a concept, and people are basically spamming papers right now to get citations from the hot topic, but the quality is shockingly bad as a result. I actually wrote to a certain physicist about one of his publications being wrong and he pretty much said he didn't care with some flowery language.
>>11891893It's because the Stokes wave has a special kind of instability which causes low-frequency perturbations to grow exponentially. It's a nonlinear effect in fluids.
