Bingo.
I wasn't involved directly, so unfortunately this is a game of telephone. This was also back in 2012 through 2015, so it's been some time. But here's my understanding of it.
Suppose the problem is to make a silicone bag that you can fill with warm water. That wouldn't be easy, but it'd be much easier.
To make something like that out of silicone, you have to pour some material into a mold, and let it sit. (I think the material was called Dragon Skin, but I'm not sure.) Think of it like cooking pancakes: You could imagine pouring this silicone into a frying pan and letting it sit, and you'd end up with a flat disc of silicone. So to make a bag, you'd want it to be a bowl. But of course if you pour it into a bowl, you'll end up with a spherical-ish disc of silicone that's flat on top, because it all pools to the bottom.
So your next attempt might be to put one bowl into another bowl, and then pour the silicone between the two bowls. That way the top bowl fixes the problem of it coming out like a flat disc. The silicone is sandwiched between the two bowls, and so you end up getting a shape that looks like the bowl on the bottom. Progress! That's closer to something that can hold water.
(Someone just told me that the shape wasn't actually the hardest part. The hardest part was materials. Dragon Skin was just one component. She said it was for the spine, whatever that means. But it wasn't the primary material, which needed to feel right and be easy to work with. I'll just note that here and continue on where I left off above. Basically, it needs to feel like skin, not rubber.)
But to get something that can actually hold water, you need it to be something closer to a flask shape. You could imagine a bowling ball inside another, smaller bowling ball, and then pouring the silicone inbetween the two and letting it sit.
Question: How do you get the silicone out? The silicone is now wrapped around the inner bowling ball. Hmm.
Once you solve all of those problems, then you start to focus on the dynamics of man-woman interaction and anatomy. That requires a mold which you can shape very precisely. I believe they ended up sculpting the molds out of clay, then turning it into something stronger through a process I don't understand.
To get the silicone out of the damn molds, they needed to invent a whole contraption that was like a giant lever. It would hook onto the inner mold and pull real hard on it, and pop! The whole thing comes out. It'd be totally impossible to pull it out with your bare hands.
Then you run into problems like, there are bubbles in the material, so this needs to be done inside a vacuum chamber to get all the bubbles out.
Finally there's the whole problem of putting a bow on it and making it look nice. You need packaging, a manual, and a reliable velcro strap that won't leak water. It needs to look professional. And all of this needs to be scalable so that when you suddenly get 200 orders because your vagina hot water bag went viral, you can fulfill those orders in a reasonable timeframe and get paid.
There's a bunch of funny stories from that era. The postal delivery people got super curious about what we were up to. (At this point they'd moved into an actual building, not the family house.) One day he found an excuse to come in, strutting around with a big smirk on his face. Then next time they went to drop off the packages for delivery at the post office, the lady there was like oh, you're the people that make the sex toys! They were like yeahhh, that's us.
It was a very interesting experience. It's a shame the business ended up folding due to lack of financing for all the production issues.