Sometimes, people message me that they spotted something in the water, but they are still determining if it was an orca.
To help people recognize an orca and distinguish an orca from other species, such as a bottlenose dolphin, we created a slide showing some information about orcas and some pictures with examples that can be confused with orcas. 
This slide is a work in collaboration with the biologists of CIRCE ( circe.info ).  
The 5 euros you will pay for it is for support of the site. Many thanks