Stylized Water 2 - Underwater Rendering (Extension)
In order to achieve the full underwater rendering feature, a variety of operations have to be performed. That said, it will not come without a performance cost, how big really depends on the hardware you’re running it on. On a GTX 1060 at 4k, the effect takes up ~0.01ms GPU time, and 0.02ms CPU time.
The performance impact is constant, no matter the scene’s complexity, but is resolution dependent. Rendering is only performed once the bottom of the screen touches the water, so it has no impact otherwise. When a camera is fully submerged, rendering for the half-in/half-out effect is skipped entirely.
On the Render Feature, you’ll find several options aimed at quality/performance scaling. If you are using a different pipeline asset per quality level, you can configure it to for lower/faster quality on some quality levels.
All options have tooltips, mouse over it to view a description.