Since the 18w15a snapshot released (I know it's late but better late than never!) my worlds have become a lot laggier than they used to be, maybe this happens because the game is consistenly calculating the color the water should have in each biome, and if that's the problem, there should be some optimizations or something.
Back to the point... Before that snapshot I had 40-50+ FPS consistenly, but now, in my worlds or in new worlds I get like 20-30 FPS, and sometimes even lower, and lag spikes are consistently frecuent.
This doesn't only apply to FPS lag, but since that snapshot I've been also experiencing strong entity lag, and drinking lag.