The Russians are putting pressure on the people of Ukraine's Mariupol and other coastal communities by moving to deny Ukraine use of the Sea of Azov:
Back ashore, in and around Mariupol, a crucial industrial port city with a population of around 500,000 that sits roughly 800 kilometers southeast of Kyiv, it has been tense since late in the spring of 2014. Russia-backed separatists briefly controlled it then before the Ukrainian military and its volunteer battalions dislodged them. Today, fighting continues to rage just 24 kilometers to the east, in the once-quiet seaside town of Shyrokyne.
I'd mentioned this in passing.
The new Russian bridge connecting Russian-occupied Crimea with Russia limits the size of vessels that can reach the ports; and a 2003 deal has enabled Russia to intercept and harass Ukrainian vessels.
Ukraine has so far not found an effective response at sea to defend themselves; although they are attempting to get economic pressure on Russian Black Sea ports through diplomacy.
Ukraine doesn't want to abolish the 2003 deal. Given that Russia invaded Ukraine, that deal shouldn't be immune to cancellation. Although I don't know if it would do any good given the power imbalance.
The question is whether Russia is attempting a creeping annexation of the Sea of Azov, perhaps with an eye on punishing Mariupol enough to get them to want Russian domination; or whether Russia is "only" pressuring Ukraine to resume supplying water to Russian-occupied Crimea.
Ukraine could use land-based anti-ship missiles as well as weapons to scatter mines on the big bridge and naval mines to return the blockade against Russian Rostov. Just in case.
