780ti temps are about half what they used to be, sit around 40c under max load in game (that's with a huge overclock boosting to about 1270mhz core!) still much more in it too.
on air would be in the low 80s even at small overclocks, and throttle the GPU boost 2.0 obviously due to that - on water dat dere max boost!
be warned though custom water cooling aint cheap, it is however a great little summer project to do and allows for massive overclocks and performance boosts! not to mention you can use most of the components in your next builds.
Also if anyone wants me 1 month old Corsair H90 hit me up I gotta sell it