Why are snorkels over 15 inches in length not recommended?

Snorkels longer than 15 inches are not recommended primarily because they have too much dead air space. Dead air space refers to the volume of air contained within the snorkel that is not actively exchanged with fresh air when the diver breathes. A longer snorkel increases this volume, making it more challenging to effectively clear the snorkel when water enters. This can lead to an inefficient breathing experience and potential discomfort while snorkeling.

In this context, dead air space can make it difficult for the snorkeler to receive fresh air quickly, as there is a greater distance between the mouth and the water's surface. A practical snorkel length allows for easier breathing and minimizes the risk of inhaling water, ensuring a safer and more enjoyable snorkeling experience.