Was having a random discussion with my girlfriend about redoing our bathroom, and all the crazy bathrooms you can see online, yet obviously not afford. We saw a giant shower—really a small room— with chaise like chairs made from stonework. I said something along the lines of “Wouldn’t it be cool to have a mesh hammock to lay in under the water” and then almost instantly made the jump to “what if you had a hammock that was a bathtub?”

She immediately brought up “ehhh I think it would get dirty real quick...” I thought it was interesting where our minds went, because my line of thinking was, “You’d need some really solid beams in the walls and probably steel cable linking it.”

I had to point out just how much water weighed, and then being myself started digging into it. What would it be made of? Initial thought was Kevlar.

Avg bathtub: 80 Gallons and 12-14” deep in the US, 18 in Europe. Who doesn’t love a deep bathtub though, so we went with that.

80*8.345lbs = 667.6lbs of water. Add in an average male and female (180, 165lbs respectively) and you get 1,012.6lbs.

As this was just a mental problem, and I’m not an engineer it (probably) went astray from there.

Kevlar tensile strength is 3,620MPa, water psi is determined by depth, not weight. 18” of water is .649psi, to MPa thats 0.00447Mpa.

.I honestly originally thought that a bathtub hammock would require some strong material. But, according to my 1 minute of research you could make it out of a grocery store shopping bad (Polyethylene HDPE, which has a tensile strength of 15MPa). Clearly something is wrong....

Where did I lose my way? What factors other than tensile strength come into play here (is it still tensile since the water is pushing down on the side of the kevlar (or whatever material) rather than pulling against it?? What materials would you use in this lavish experiment? How would it be implemented (how the support cable attaches to the hammock so it doesn’t just rip off a piece, etc, or other thoughts)?

If you’re going to build a bathtub hammock, honestly build a bathtub hammock. So for this question lets assume the bathtub is 120 gallons and 22” deep. Include the weight of an average male, average female and at least two glasses of wine.

TL:DR: See title, and last line.

EDIT: Found this Bathtub Hammock online. While admittedly awesome, we wanted something more true to a hammocks function, not only its form. What material would be strong enough for this application, but still “fabric-ey” (excited to learn the materials engineering terminology for this) enough to be a hammock.