I totally solved the bathtub size issue. The shape was wrong and Japanese had it right. I am 72 kg and 177cm. Very economical too, with 20 liters I can totally submerge. https://photos.app.goo.gl/HDwDf1s4PD3KoW3c8
Anyways one should check the barrel at the junkyard. If you can get in, it is easier get out because the water is lifting you.
Wait, really?