Israel per se has fuck all to do with this, to be honest. Attacking a foreign flagged civilian vessel is a big deal, especially when the eyes of the world are upon you and you cannot declare something to have happened on the fog of war. There’s an American P-8, which is an intelligence as well as an anti-ship/anti-sub plane, covering the ship. No one knows what it’s rules of engagement are, but the implication is that it’s there to defend the civilian ship. Attacking the US plane would be an act of war. Attacking the ship may trigger the American plane to defend it by launching weapons against the attacking vessel.
The one thing that the Russians could legitimately do is block the ship physically. They can play chicken by threatening to steer into it, but I can’t think that they’d risk widening the war at this point. No shade on Ukraine - this one is going to go down as one of the greatest victories in the history of warfare - but if they can’t make progress against Ukraine then NATO will go through them like crap through a goose.