Nobody has ever seen a live colossal squid swimming so this is a difficult question to answer. The scientists had to look at how other closely related squid swim and come up with a theory about how the colossal squid moves.
See how scientists think the colossal squid moves in this video:
Cranchiids or glass squids
Colossal squid are part of the Cranchiidae family, known as the glass squids. There are many videos of squid species swimming, including the glass squids.
Cranchiids or glass squids have a very different outward appearance, or morphology, to most squid. They have forward-facing eyes which gives them binocular vision. This also means they cannot hold their arms out directly in front as they wouldn't be able to see! Most other squid have eyes on the sides of the head. They do not have to lift their arms out of their field of vision and can swim with their arms flat.
Cockatoo position – or not?
Most of the time cranchiids hold their arms either up over their heads in the ‘cockatoo’ position, or down in the ‘reverse cockatoo’ position.
Scientists think that the colossal squid, like other cranchiids, does not usually swim with its arms held flat out. But there is on-going debate about whether the colossal squid swims in the ‘cockatoo’ position or
The team reasoned that if the colossal squid held its arms up in the ‘cockatoo’ position, the lower arms would be longer, as they would have to reach further to meet the tips of the upper arms. Careful measurement of the colossal squid's arms showed that the lower arms are longer. The position and direction of the non-swivelling hooks on the arms also suggest that the colossal squid uses the ‘cockatoo’ position.
However this is all just a hypothesis – until someone sees a colossal squid swimming we won't know for sure. This is the process of science!