MrClass wrote
I mean how could one ever survive a blackhole and reach singularity (the most dense and most gravitation heavy part of a blackhole) without being subject to spaghettification, then gets spit out of it (which is impossible, unless you're moving faster than the speed of light and in the opposite direction of the singularity), and still survive?????
It's because they were approaching a supermassive black hole and not a stellar black hole. A supermassive black hole has very shallow tidal forces due to it's size and would not rip you apart if you moved around it. Also, he never reaches singularity, but approaches it. The future humans transport him into the tesseract where he can access time without a strict linear constraint. After he transmits the data to Murph, the future humans take him back out of the tesseract.
MrClass wrote
Don't get me wrong I did enjoy some parts of the movie like the huge tides (which could be true in case an external source of gravity is affecting that planet, but yet again how were the characters walking normally on the shallow water).
For the same reasons the moon only affects the tides on Earth and not the people standing in the high-tides, the black hole's belt only affected that planet's tides. Liquid is more dense (and therefore has more mass) and is more gravitationally attracted than solids.
Although what was not realistic is the fact that there were such huge waves in the first place. A supermassive black hole would not have such a pronounced effect on the liquid on the planet. Only a stellar black hole with much stronger tidal forces would.
EDIT: Oh, also, I think I remember two waves on that planet. Those weren't actually waves, they were just incredibly high tides coming in. And if that's the case, that means that planet rotated in a matter of minutes. So a day on that planet is a couple of minutes long?