I know that the version is just a pre release but the kelp is VERY laggy, or at least something is.. It's not just me that experiences this lag, even youtubers experience it. 

The reason why i blame kelp is because, every time kelp grows i get lag spikes (idk if this helps or something but.. single player world, ave. FPS is 120 + ) I think it's because of the animations and how much kelp there is in the ocean/sea..