Squid have two gills, one on the left and on the right side of their heads. The gills are part of a squid's respiratory and cardiovascular system. They are feather-like organs used to collect oxygen from water passing through them.
Squid have three hearts. Connected to each gill is a branchial heart that pumps blood into the gill. These two smaller hearts connect to the larger heart, which distributes oxygen to the rest of the squid's body.
Most squid do not exceed 24 inches in length, but the colossal squid grows up to 46 feet. It is possible that the myth of the kraken came from seafarers' sightings of colossal squid.