You can tell some one is on water usually by looking at edge temp, hotspot would be harder unless the user put on PTM7950 cos any bad thermalpaste will give really high hotspot temp, cos AMD dies aren't perfectly flat and output lot of wattage which causes pumpout over time, which is why you get good results on day1 but bad results after couple more days weeks or after a month, instead of repasting all the time i suggest trying PTM7950 so you never have to do that again.
I am on kryosheet... I am good for years now, the pump out problem is pretty severe, everyone should understand it. I've used on paste the card for two weeks(before the kryosheet order shipped in, it took a while) and my MX6 was already starting to move out... my max hotspot temps under heavy OC and benchmarks is around 70C(went down from 83C), while the core is about ~45C. The added pad thickness also is a plus here. My loop water temperature is usually around 38-40C during long gaming sessions, I like my PC silent, no need to spin up those fans that much. While playing Starfield I am 44C core and 60C hotspot max for example.
Next thing to add... depending on the waterblock we each have... don't gimp on cooling other parts. I've smeared thermal putty all over the the RAM and VRM sections, especially all gaps in between ram(thermal pads cannot do it, it is very important, you gather more surface using IC side walls) and chokes... it is 500W+ card... it needs every bit, I mean I have put really a lot of it. There are blocks that are skimping on cooling chokes... don't be that guy. You can use thermal pads, but with so many parts you never get those right thickness sized to have the GPU mount pressure right.
Before I had problems OCing my Samsung VRAM... now I am memtest vulkan stable at ~2700MHz, before it struggled on ~2625MHz...
So Kryosheet and PTM7950 are the only good solutions for these cards, don't fool around pasting the card with conventional pastes. The China knockoff PTM7950 are actually not that bad also, they reverse engineered it well this time.
