I did my own models and shaders (I actually wrote my whole render pipeline on my own), but stock sound and composited together stock textures (targets use a baked composite using custom masks, terrain uses splat mapping and distortion). I focused mostly on my shaders, using some quick placeholder primitives as assets until fairly late in the jam.
I ended up creating what might be the first-ever non-RTX game to feature physically-accurate water refraction, effect which involves a lot of custom vertex and lighting shaders and a pipeline organized around them.