Here is what happened today:
(BBC summary here: https://www.bbc.com/news/world-europe-46338671)
The Ukrainian navy tried to do a freedom-of-navigation operation and transit through the Kerch straits.
The Ukrainian flotilla consisted of two of the new Gurza-class gunboats, and one tug.
First, a FSB craft rammed the Ukrainian tug, causing damage. You can see a video of the ramming here. I am not a seaman, but it seems to me like a pretty clear-cut ram, with the Ukrainian tug stopping (perhaps to avoid the other FSP ship in front of him) and the much-larger Russian ship evidently turning to ram the vessel head on.
You can hear the Russian commander shouting “hit him on the right! Hit him on the right!” along with copious cursing.
Then, and the precise events are not clear yet – Russian ships opened fire on the Ukrainian warships and reportedly boarded and captured the warships. There are reports this happened in an area of the sea of Azov that even Russia calls “international waters.” Six Ukrainian sailors are said to have been injured, two seriously. The crew’s status is unclear.
This is a clear act of war.
Russia has also moved a ship into the channel under the Kerch bridge, blocking any further traffic. This is a de-facto blockade of Ukraine’s eastern coast, another act of war.
This is a serious escalation. Russia just engaged in naval warfare, capturing Ukrainian sailors.