So most baths have some sort of overflow “safety” drain or hole that is located (depending on your tub) somewhere under or near near the faucet. While this IS good for safety, it is horrible for getting the water level of your bath tub very full. Our tub also loses so much hot water that its hard to keep the water warm. In an old apartment, I once caulked the hole shut but for the life of me can't find that product which worked pretty well (but was permanent and couldn't be removed). After googling pretty much every word combination I could think of, it came down to a few options to try: Porcelain or chrome plates. You can screw over the overflow drain (if you have one that fits exactly). Not ideal if you aren't handy or sure whether it will fit. But if you own your place, these look nice. They are also permanent, so if you have kids I would not recommend it, but there are some good examples at Vintage Tub and Amazon. Sugru. Sugru is really cool — it's not made for this purpose exactly and we're not sure if it will work, but we're intrigued with this stuff and would have tried it if we didn't find the next solution. It's also more colorful than we wanted in the tub. "Deep Water Bath". This is the product we ended up buying. It's just a piece of 4" diameter vinyl with suction cups that fits over the drain hole. It's perfect because it's a temporary fix and you can remove it — and it also does still have a drain hole which you can rotate to the top. So if you absolutely had to leave the room and then forgot you were running a bath, it would still drain the water out (just at a much higher level). It looks like it will fit just about any drain because it isn't snug, although it works great. As you can see from the photo above, we gained an insane amount of water in the bath and if we fill it up and get in, it is right at the top of the bath so our knees actually get wet.
We got our Deep Water Bath at Amazon for about $7. Images: Jeanine Brennan