Hiding ocean while inside vessel, (common problem, but finding no solution) -- UE5.3 crashing on some approaches

Working on a VR shortfilm in UE and we’re near the finish-line but have a problem that keeps cropping up that’s a very common problem but the typical solutions don’t seem to be working for us.

Short version:
There’s a materials/FX issue that we just CANNOT get solved and everyone we’ve talked to has hit a dead end on it without a major overhaul. Entire film set inside a vessel with windows, that at one point submerges into an ocean. So that whole depth sorting thing where ocean surface needs to be hidden inside the vessel, show the underwater stuff, and as the vessel submerges, we need to be able to see underside of the water through the windows. I’m starting to lose hair over this issue, which has been plaguing us for going on 2 years now!

Here’s a video of the issue which also probably describes my needs better
https://vimeo.com/867506410/f4a82dc7c7?share=copy

More info:
We WERE using the Environment Project Ocean plugin and UE 4.26 and had kind of hacked a mostly-working version of this, but it’s wonky and terrible performance-wise, and renders inconsistently (sometimes elements are visible, sometimes they aren’t, with no clear changes to anything).

Now we’re seeing if it makes more sense for us to switch to 5.3 and have mostly had good luck, but the Environment project is even more wonky in UE5. So right now we’re trying Waterline Pro but there seem to be even fewer options for masking out the water surface without some super hacky approaches.

I may have a potential START but UE keeps crashing when I try it out.

If this seems to be a huge issue we’re potentially ok hiring a short-term freelancer to work on the materials/fx for this but stubbornness is making me want to solve this problem myself (I mean… with advice from the forum!)

Help?

Quite old solution to this (probably there are better now):

  • create water plane with hole around your vessel and move it together with ship.
  • make water use world uvs this way while water plane moves all waves stay put, they will be rendered using world coordinate.

This does not work for multiplayer games.

I might not completely be understanding, but the ship is not always on the surface of the water. It starts above water, then submerges. Also the hole would need to be shaped and sized exactly to the vessel, which is an odd shape, AND because it submerges, the “hole” shape changes with the ship going under