Amazon River Dolphins or Botos (Inia geoffrensis) Mother and Calf underwater in Flooded Forest, Rio Negro, Amazonia, Brazil
The biggest specie described in the World , published in 2010.
Paper: http://www.scielo.sa.cr/pdf/rbt/v58n4/a06v58n4.pdf
This observation was made with Brian Kubicki, Federico Granados, Cristian Herrera and Allan Solano.