Unity Volumetric Water Test
Over about the course of 2 years over on twitter, I've been building various systems that have been working towards this - water surface shaders (modelling refraction, reflection, chromatic aberration, caustics, etc), volumetric lighting effects (from god rays to full volumetric fog), and more recently a screen-space AABB that can be used to efficiently render volumes from both outside and in. Put together, you get this - place a single cube in the scene, attach the script and model to your liking.