I added these to my existing launch options and the issue seems to be fixed for me.
+mat_picmip 2 +r_rootlod 2 +mat_reducefillrate 1 +r_waterforceexpensive 0 +r_waterforcereflectentities 0 +r_shadowrendertotexture 0 +mat_trilinear 0 (lowest settings)
I thought these commands were useless?