The problem with brine from desalination is that it kind of behaves like a heavier liquid, sinking to the bottom. That causes it to stay together, taking longer to mix with the regular ocean; and the coastal seafloor there is a lot of life that doesn't appreciate water with double the salinity of regular ocean.
To solve that you can just dilute it more, either mixing with some other waste water stream or by releasing it over a larger area rather than a single outlet.
> Modern desalination plants generally recover about half of the intake flow, which means their brine stream is about twice the concentration of normal seawater.
I imagine this heavily depends on the actual plant design though. Also because of the above mentioned issues you generally don't discharge it like that but blend it with other water.
To solve that you can just dilute it more, either mixing with some other waste water stream or by releasing it over a larger area rather than a single outlet.