"A submerged breather"

No need to worry, that thing coming out of the water isn't a monster, it's that guy's tail! He can breathe through the mouth on it, and he likes swimming, so he sometimes uses it like a snorkel. Though, he tends to not do that in lakes and the ocean, since people might really think it's a monster. There's already been a couple "monster" sightings he thinks might've just been him...