It depends on what kind of poison you're talking about. On a scale of from 0–100, with 100 being the most painful, drowning comes in it 79. read more
Drowning in freshwater is different from drowning in saltwater. In fact, more people drown in freshwater than saltwater. Around 90% of drownings occur in fresh water, such as swimming pools, bath tubs and rivers. read more
On the other hand, fire causes pain. Thus, in terms of physical pain, the question is already answered: death by fire is painful, death by drowning is not. Psychological pain should also be taken into consideration and involves the experience of panic. read more