Why are snorkels longer than 15 inches generally not recommended for diving?

Snorkels longer than 15 inches are generally not recommended for diving primarily because they can have too much dead air space. This dead air space refers to the volume of air within the snorkel that is not involved in the breathing process when a diver is underwater. If the snorkel has excessive dead air, it makes it harder for a diver to breathe efficiently.

When a diver uses a snorkel with significant dead air space, they first inhale the stale air from the snorkel before drawing in fresh air. This can lead to increased carbon dioxide buildup in the lungs, which can cause discomfort and can even impair the diver's ability to function properly underwater. For optimal breathing and safety while diving, snorkel sizes that minimize dead air space are preferred, ensuring that a diver can draw fresh, clean air with each breath, supporting their safety and comfort during the dive.

Other considerations for snorkel design, such as storage issues or weight, are secondary to the critical impact that dead air space has on a diver’s ability to breathe effectively.