Reality is not as dramatic, fortunately. After annexing Crimea, Russians have de-facto assumed control of the Kerch strait, which is the only way out of the Azov sea. Their goal seems to be to effectively land-lock a large part of Ukraine which will lead to a big economic hit for steel-exporting cities in Eastern Ukraine. Legally according to maritime law and treaties they they have to let the Ukrainian ships pass through, but in recent months they started demanding inspections or closing the strait under clearly made-up reasons.
3 small military ships of Ukraine were going from the port of Odessa on the Black sea to Mariupol on the Azov and when they reached the strait, Russians said it's closed for "maintenance," even though they were letting Russian ships pass through. Then the Ukrainian boats informed them they are going to pass through anyway – and when they tried to do so Russian military ships opened fire (6 Ukrainian sailors were injured, 2 in critical condition) and rammed one ship, eventually taking all the crews prisoner.
This was all captured on video by the Russians themselves, you can hear the Russian captain very excitedly ordering them to ram the small boat:
UN Security council meeting resulted in a strong rebuke of Russia's actions from the other members; Russia's argument that all this was done for "safety reasons" was laughable on its face. Domestically, after 2 days of heated deliberation, Ukrainian parliament declared martial law for 30 days in every region bordering Russia and Russia-occupied territories, but it's not clear specifically what that would accomplish. It's bad, but at present there is no reason to think that a large-scale war is on the horizon.
What makes this conflict different from the "hybrid war" in Donbas is that this time the Russian navy under the Russian flag was shooting at the Ukrainian military personnel - not the mysterious "green men" or "Russian-backed separatists." So even though in terms of casualties this conflict pales in comparison to far larger and deadlier battles of the past few years, an important symbolic line has been crossed.