There are a lot of great resources scattered across the web, but one particularly interesting one, is a great documentary shot with local scientists and divers around Seattle titled: Searching for the Mystery Sharks of Seattle

The Seattle Aquarium has done research on Sixgill sharks. These are three papers that they have published with open access.

Sixgill Conservation Genetics 2010

Sixgill Abundence 2014

Sixgill Bite Kinematics 2016

This is a short video of Sixgill sharks off Honduras, and it includes some information about the species.

There are a series of videos about searching for sixgill sharks, and the videos features the Seattle Aquarium!

Sixgill Sharks - Into the Abyss - Success at Last

Sixgill Sharks - Into the Abyss - The business end of a Sixgill

Sixgill Sharks - Into the Abyss - Shark Monitoring Station

Some good video while the voice-over gives you good shark facts! The video page also has quite a few links to other sites with information:

A short video from NOAA Sanctuaries about the Bluntnose Sixgill shark. It has video from the Nautilus expedition

The Wikipedia article on Bluntnose Sixgill Sharks is somewhat short, but also has some good links to information.

A short story from KOMO TV about Sixgill Sharks brief history in an aquarium in Seattle

A TV documentary about rescuing a sixgill shark from a fishing line in Bermuda. They take some DNA and put a tracker on the shark.

This is a diagram of the various fins on a shark. Sixgill sharks do not have a primary dorsal fin, but they do have a secondary dorsal fin.

https://commons.wikimedia.org/wiki/File:Shark_finning_diagram.svg