Otter tracks are not always as clear as the wildlife books and field guides suggest
Although otters have five short toes very often only four of them leave an imprint.
In these tracks you can just about see the imprint of the fifth toe on the last track in the image below. It's probably the left hind foot.
Finding fresh tracks in the sand is just as exciting as seeing the live animal, you know it has been there and you haven't disturbed it.