Depending on water temperature (so you’re not burning energy to maintain body temp), salt vs fresh (you’re more buoyant in saltier water), and body fat composition (fat adds to your natural buoyancy), I can definitely see someone who’s in decent shape managing 10 hours. I think the record is over 100 hours, so 40 is definitely going to be well above “normal” but not necessarily superhuman.
Now just imagine how the hype is for literally everything they’ve ever done, and it’s on the exact same level. Once Tesla/Musk does something related to your field, it’s abundantly clear what an absolute fraud he is.