@talk72000,
In a relativistic environment there are seven states to matter (Fermionic Condensate, Bose Einstein Condensate, Solid, Liquid, Gas, Plasma, Fusion Plasma), so if the ball can't burst - well eventually if you put enough energy into it surely the water will reach a Fusion plasma state.
Water will significantly compress - provided you subject it to pressures that start to approach nuclear fusion. Enough pressure will start nuclear fusion - so if you heat this ball enough you will create a fusion reaction with the water inside it. Mind you put that much energy in and the water will likely ionise into atomic hydrogen and atomic oxygen - but you get the same end point - a fusion reaction - changing everything inside all the way up to iron eventually - given your ball is tough enough and you keep putting energy in!
Of course if your iron ball can't break -put enough energy into it and you'd eventually create a singularity, but then you're dealing with non relativistic states of space time...
