Quality and performance decisions
If you wish to improve the performance of your project that includes a water surface, there are several adjustments you can make.
Script interaction
Don't enable this setting unless you intend to use water height data in scripts. When you enable script interaction, it increases the number of calculations Unity performs because the simulation runs on both the GPU and the CPU.
Levels of Detail (LODs)
In the Water Volume Override, you can reduce memory demands if you keep grid size down. Reduce the Max Grid Size and Elevation Transition. You can also lower the Num Levels of Detail (number of Levels of Detail).
Tessellation
You must enable hidden properties to see the Tessellation options, which are on the Water Volume Override. Reduce the Max Tessellation Factor, Tessellation Factor Fade Range and Tessellation Factor Fade Start to save memory.
Fade ranges and Simulation Bands
Water surface types with more simulation bands have higher memory requirements. This is why an Ocean, Sea, or Lake surface requires HDRP to do more calculations than a Pool. The Start value determines where HDRP begins to fade out the contribution of a Simulation Band. One way to offset the performance demands of Ocean, Sea, or Lake surfaces is to lower the Start value. This begins to fade out the simulation band effect closer to the camera. Then reduce the difference between the Start and Distance values in the Fade Range for each band. You must enable hidden properties to see the Fade Range settings.
Smoothness range
Smoothness values determine the distance from the camera at which the water surface becomes less detailed. In addition to the same Fade Range properties as the Simulation Bands, Smoothness has Close and Distant properties. As with Simulation bands, you can save memory by reducing the difference between the Fade Range values, but you can also reduce the Close and Distant values. You must enable hidden properties to see the Fade Range settings.
Refraction strength
The Maximum Distance property determines how far into the water surface HDRP renders the Refraction effect. Reduce this value to conserve memory. This also reduces the visibility of the refraction effect.
Resolution
You can also specify lower resolutions for masks, decals, caustics, and the simulation to save memory. See Project Settings > Quality > HDRP for the Simulation Resolution property. The Caustics properties include Caustics Resolution. For masks and decals, custom mesh and custom foam textures, adjust the resolution of your source files.