[blutack]

Presumably also open circuit not rebreather given this was mid 90s. It's a pity the article doesn't detail their dive plan, the gas quantities must have been staggering.

Nowadays this type of diving would be done using an eCCR (and backup open circuit), where some software on a microcontroller controls the amount of oxygen in a breathing loop. A scrubber (hopefully) removes the CO2. Changing the gas mixture as you go is required to reach these sorts of depths because oxygen becomes toxic at pressure, and gas density itself can cause issues with breathing.

[mi100hael]

There's more detail on the dive in this account: https://cambrianfoundation.org/2000/02/28/1995-expedition/

[eszed]

This one says twelve minutes of exploration at the bottom.

[nradov]

Right, Terrence Tysall and Mike Zlatopolsky (Zee) dove the Edmund Fitzgerald in 1995 using open circuit gear. This article by Tysall gives some details of their dive plan.

https://advanceddivermagazine.com/articles/fitz/fitz.html