You can often see a pic of a 'smiling' otter in any meme fest online.
But other than being oh-so-cute, otters are a valuable part of the world's ecosystem.
The day, celebrated on the last Wednesday of May, underlines the need to protect otters.
According to Connecticut's Beardsley Zoo, there are 13 species of otters. Twelve of them are on the decline.
Otters are indicator species. This means their presence is a measure of how healthy an ecosystem is.
We need to take it upon ourselves to help conserve these cute mammals.