pubmed.ncbi.nlm.nih.gov/26046678/

A bathtub drowning is one of the leading causes of death in a bathtub. The purpose of this study was to evaluate how reliable the drowning-related signs could be for identifying a bathtub drowning in the cases of death in the bathtub. Performing a retrospective review of 92 deaths in the bathtub in Maryland, 71.7 percent were the presence of bathtub drowning and 28.3 percent were the absence of bathtub drowning. Three leading contributory causes of death were cardiovascular disease, drug/alcohol-related death, and seizure disorder in both groups. There was a statistically significant difference between the groups in relation to a history of recovery from the water (95.5% and 38.4%, p<0.001), foam in the air way (33.3% and 15.4%, p<0.05), watery fluid in the sphenoid sinuses (81.8% and 11.5%, p<0.05), hyperinflated lungs (36.4% and 3.8%, p<0.01), and watery fluid in the stomach contents (40.9% and 3.8%, p<0.01). More than triple overlapped drowning-related signs could be beneficial for the diagnosis of a bathtub drowning. A comprehensive investigation incorporating a thorough scene investigation, gathering of the victim’s medical and psychosocial history, and a meticulous full autopsy is necessary to elucidate both the cause and manner of death in these cases of death in the bathtub.

So there are usually contributing factors like age, alcohol/drugs, or other medical issues. So ask yourself this: Can you be certain that you will never have a medical issue in a bathtub that might lead to you drowning? Have you ever bathed while drunk or high?