Right now the water we have is very see through and clear with a very faint tint of blue. It makes it hard to convey different colored waters even when using various methods like glass underneath because no matter what at the end of the day it is still the same old water. That is why I propose a pack of new waters be introduced like through the recube store.
There could be tropical bright blue water, a dark blue water to convey depth, and a muddy brown water for example. Maybe even some fantasy inspired waters like a pink or green.