This is how items behave when using Sinking Items. This fixes the jankyness as shown in the WITHOUT gif.
This is how items behave when a 1.13 or newer client is connected to a 1.12.2 or older server which is running ViaVersion.
Makes items sink in water just like they did before the "1.13 Aquatic Update". Intended to be used on 1.14.4+ clients connecting to a 1.12.2 server or below.