it wouldn’t become a black hole. black holes only come about when a extremely large star (much larger than the sun) goes supernova and leaves a black hole in the middle.
If you had a body of water larger than the sun suddenly hitting it, it may indeed shorten it’s lifespan, but the interaction between this water-planet and the sun would be very cool! I also wonder if the pressure in the middle of this giant water planet would be enough to strip the hydrogen (‘H’ in H2O) out, and start it’s own fusion reaction, so create another star, essentially.
A squirt of water fired at the sun wouldn’t get very far – it would essentially boil in the vacuum of space – as you go up in altitude, which means down in air pressure, the temperature at which stuff/water boils goes down. So if there was no air rpessure, it would instantly boil!
For the larger-mass-than-the-sun blob of water, lets assume it doesnt boil off – what would happen if they collided?
We’re saying space wouldnt boil it, but the Sun definitely would. It would also break the bonds between the hydrogen and oxygen in each water molecule. Im going to say that the hydrogen would join the body of the sun, and take part in fusion at some point.
What would happen to the oxygen? Oxygen collects at the centre of a star after it has gone through the helium phase. Im not sure if it would break up the oxygen, and let it burn for longer with more hydrogen, of if it would collect in the middle.
Either way, I think the lifespan would decrease, seeing as it has (at least) doubled in mass, this means it would burn more fiercely and over a shorter time.
I really like this question, and I wish I could answer it more exactly – I think you should post it on this website: https://what-if.xkcd.com/
This guy, Randall, is a physcicist, and answers questions from people just like this, except he properly researches it, and gives you a solid answer.
Id like to see how close I was! 🙂