Turn The Overflow Plate Upside Down

One D.I.Y method that can add a little extra depth to your bath is simply to unscrew the overflow plate and turn it upside down. The opening is then at the top, allowing for a little extra water.

This isn't going to make a huge difference, but it's a quick simple temporary solution, until you get around to buying a cover or even a new tub.

Another D.I.Y technique for blocking the opening is to use Saran wrap and duct tape. It sounds sketchy and I haven't personally tried this myself, but apparently the pressure of the water holds the wrap flush against the side of the tub, minimizing any leakage. It's obviously going to look quite unattractive. However, I couldn't care less as long as i was avoiding shallow baths and annoying gurgling sounds.

Another material which has been mentioned is 'Sugru', which is a silicone based version of modelling clay.

However, the specialized covers previously mentioned in this log are relatively cheap and easy to pop on and off, so seeking out permanent gap fillers is a little unnecessary.