Once I went out snorkeling and had a hard time getting back because of the current. I exhausted all my energy trying to fight the current and was really running out of breath while panicking. Even though I had a snorkel, I was afraid I was going to drown since I was really pushing the limit of how fast you can breath through that tube. Fortunately I regained some presence of mind to just relax a little until I calm down and then try a slightly different route.