Ukraine has already largely neutralized Russia's ability to control the western part of the Black Sea.
This is stated in the June 21 British Intelligence review of the war in Ukraine.
It recalls that on June 17 Ukraine claimed to have hit a Russian ship off Zmiinyi Island, the target "almost certainly" being the Russian tug Vasily Bekh Rescuer delivering weapons and personnel to the island, and this was the first successful use of Harpoon anti-ship missiles provided by Western partners.
"The destruction of a Russian ship with a supply mission demonstrates the difficulties Russia faced in trying to support its military occupying the Zmiinyi Island...The ability of the Ukrainian coastal defense largely neutralized the Russian ability to establish control of the sea and deploy forces in the northwestern part of the Black Sea. This thwarted the initial operational plan of the Russian invasion, which envisioned a threat to the Odesa region from the sea," the review noted.