Two Brazilians who were filmed tormenting an enormous anaconda and dragging it through the water in a boat have been fined.

The pair were each fined $1400 on Thursday by environmental authorities in the Mato Grosso do Sul state in Brazil's southwest after they were alerted to footage of the 2010 incident, Correio do Estado reports.

The incredible video shot by a woman on the boat with her husband and another man shows the bloated Yellow Anaconda repeatedly trying to swim away from its tormentors.

The huge bulge in the reptile's body suggest it had recently devoured a large animal whole, possibly a capybara.

The woman on the boat shrieks in fear as a man at the front of the vessel reaches into the water and pulls the giant snake, which is at least 5m long.

The trio's lawyer argued that while they had been negligent they had no malice and the anaconda was not hurt.

They have 20 days to appeal the fines.