Humpback whales do not use Listerine.  If you are upwind or one (or more), you will know it by the smell.  When they exhale through the blowhole, a very aquatic aroma is shared.  This isn’t the only way to spot them of course, they are a pretty large beast so not the hardest thing to find – particularly if it is a calm day like it was for us.  We saw so many humpbacks that we passed most of them by.  We did end up pretty close to some, though.  These guys seemed totally uninterested in us.  I have to say I took it hard.