Disabling vsync helped with the lag but then scrolling though hotbar registers way too many times and it keeps going like a wheel of fortune. Setting minecraft to run under 'power saving' mode which forces using the onboard graphics removes the lag though.
Seed 1442558868 at 11,49,-1
[media]Was able to get this snow underwater bug to happen by falling through snowing effect near an iceberg.
It was raining and I fell from about 50 blocks through a transition to snow into the water pool resulting in the snowing effect playing under water.
After the 1.16.200 update, scrolling causing the hotbar to cycle serveral times when in 'full screen' mode. But changing to windowed mode, the scroll works as expected.