Answer:
The most appropriate answer would be "Respiring while swimming underwater".
Anaerobic respiration refers to the breakdown of sugar in absence of oxygen.
It results in the production of energy (less as compared to aerobic respiration), alcohol, and carbon dioxide.
During underwater swimming, oxygen supply is decreased in our body due to which muscles switch to lactic acid fermentation which is a type of anaerobic respiration.
In lactic acid fermentation, muscles convert glucose into lactic acid and carbon dioxide is produced as a byproduct.
It only produces two molecules of ATP per glucose molecule.