If they can take out the Kerch strait bridge that be comes a possibility. But that also depends on the offensive capabilities of the Ukrainian Army.
Taking Crimea would be a major operation and the Ukes need to make sure they have enough troops to hold elsewhere and take Crimea too.
Cutting off the Kerch strait bridge and other supply routes and cutting the water supply would put Russian forces in Crimea in a severe bind. Of necessity, relief or evacuation of Crimea would then become the focus of Russia’s military effort in the region. In effect, Russia would be forced to take offensive action on unfavorable terms, just as Nazi Germany desperately tried to relieve its troops in Stalingrad when they were surrounded.