Gaghiel is the Sixth Angel, and is the only Angel to attack a target other than New Tokyo-3. It is encountered by the UN Pacific Naval Fleet during transport of Evangelion Unit-02 from NERV-03 in Germany to NERV Headquarters in Japan.
The Angel's primary habitat seems to be underwater, although it does have the ability to jump to the surface. Its physical body is enormous, dwarfing even the Evangelion Units. Despite its size however, it is highly mobile and highly maneuverable underwater. It also does not appear to have any special attacks, instead utilizing its sheer physical size to inflict damage on its targets. Nearly a third of the UN Pacific Naval Fleet is lost to such attacks. Underwater, Gaghiel also uses its giant teeth to attack Evangelion Unit-02.
Gaghiel's defensive capabilities are for the most part untested, though its Core is hidden inside its mouth cavity, making it difficult to assault directly. Its AT Field is however strong enough to resist conventional torpedo attacks.
The Angel is ultimately defeated after being hooked like a fish on Evangelion Unit-02 and its Umbilical Cable. NERV Operations Director Misato Katsuragi orders to evacuate and sink two Iowa-Class battleships (the Illinois and the Kentucky) in line with the Umbilical Cable. With Evangelion Unit-02 partly swallowed, it is able to neutralize Gaghiel's AT Field and force open its mouth, allowing the two sinking battleships to enter its mouth cavity and destroy the Core.
While NERV claimed the Angel's goal was to destroy Evangelion Unit-02 during transport, its true goal was obtaining the contents of Ryoji Kaji's case, which he was smuggling in from Germany to NERV Commander Gendo Ikari. The contents of which, was the dormant embryo of Adam, the First Angel.