A bait ball, or baitball, occurs when small fish swarm in a tightly packed spherical formation about a common centre. It is a last-ditch defensive measure adopted by small schooling fish when they are threatened by predators.
Octopuses have blue blood. To survive in the deep ocean, octopuses evolved a copper-based blood called hemocyanin (rather than ours, which is iron-based) which creates a blue color. -- 22 Octopus Facts That Are Definitely Worth Ogling