A brain is like a computer, and dreams are just data garbage collection. The brain will gather all the segments of disconnected data it hasn't processed yet and piece them together, seeing if anything fits. Most of the time it doesn't. The dreams that are remembered are the most closely-fitting.
Humans sleep and dream a third of the time. Some living things dream much more than this, some much less. Plants dream in chemicals rather than sensory impressions, but other animals dream like humans, give or take.
Whales are always waking and dreaming at the same time. While a human brain is like Windows, needing a distinct defrag period as opposed to its usage sessions, a whale's brain is more like UNIX or Linux. One-half of a whale's brain is sleeping and dreaming in the background while the other half is awake, processing new input data and providing output.
The bowhead whale can live over two centuries. Two centuries of dreaming paired with two centuries of continual wakefulness. Two complete centuries of letting in the world and dreaming it out, imagination and wonder fed nonstop with new cues from reality.
At best, human brains provide workstations. Whales get servers with one hundred per cent uptime.
Very recently, in about a quarter of a single bowhead whale's lifetime, humans have figured out how to expand brain wakefulness and capacity artificially. Machines have been built which never sleep and which complete their data garbage collection in the background. They are connected by wires and can communicate over thousands of kilometres, the same way that whale song can be heard from one end of the ocean to the other.
Is a yawn just a sped-up version of a humpback's call?