shortness of breath #1. If you were feeling a bit short of breath, just stop. Take the snorkel out and see if you recover. If not, just slowly paddle back to shore and rest. Knowing if you have pulmonary edema or not is impossible short of a chest X-ray, but you would likely have shortness of breath as primary symptom. In fact, I believe the gentleman took his snorkel out and said he felt he couldn't breathe.

For him, he likely had tiny reserves (everyone has reserve in their lungs if you run into pulmonary edema) but most of us have large reserves. The more obese you are the smaller the reserves are, it is HUGELY different when you are obese vs healthy weight.