almost no spawns for render distance 8 and under

i found that all my farms that included mobs would be almost 10x faster if i set my render distance to 10 or above, luckily im able to keep it on render distance 10 because 1.13.1 is much more optimized, good job mojang! but anyway i work in the ocean and now that i have my render distance to 10 loads more drowns are spawning.