I am only just starting out, I have another thread where I am asking for advice see Bath Fizzy Questions. My first batch had 300g bicarb and 100g citric acid. I spritzed with water and added a few drops fragrant oil and dye. I added too much water and the bombs were expanding and becoming misshapen. BUT they certainly floated. The only one I have tried so far shot across the bath to the end of the tub. On advice from others I have a batch ready for testing tomorrow, but I added another 50g to the citric acid, and I ditched the water for witch hazel.
You might get advice from others who are more experienced but If I were you, I would try leaving out the clay and the cornstarch, one or both may be causing your bombs to sink.
Hi cgsample, if you google "bath bombs" you might find some videos that show them in operation. Basically they are ball shaped (usually), you throw them into a tub of warm/hot water, they fizz, they can give colour and fragrance and make the water feel nice on your skin.