A child aged 2 years and 6 months may be an accomplished walker, or on the other hand have been only walking for a few months. Developmental milestones vary. They fall, stumble and topple easily and frequently when attempting to change direction or encounter a tripping obstacle.
They would have minimal sense of direction and no trepidation or awareness of hazards such as water.
I would say that unsupervised for even a few moments, in the proximity of a pond or even a bucket of water, a child of that age could drown.
Likewise, unsupervised in a bath etc, the same thing applies.
Sue