Scientists suggest that humpback whales sleep with half of their brain still active. They are said to be "logged" or "logging" whilst sleeping at the surface. This is because as they rest they resemble a log floating. I personal have witnessed humpbacks sleeping, the mother was in an inverted vertical position, and stayed this way for more than 25 minutes as her newborn calf swam around close by, never wandering further than 10 meters away. This whale did not move even with the noise of the 2 stroke out board motor when we slowly approached staying a couple of hundred meters away at all times. We watched as the mother came to the surface after 25 to 30 minutes, took a couple of breaths and resumed her inverted vertical position again. It was not long after that both mother and calf swam south to continue their migration back to the Antarctic waters.

Humpback Whales Sleep

Whales Voluntary Breathers

Humpback whales like other whales and dolphins are voluntary breathers
so they have to be awake to come to the surface to breathe. This means that
they can only sleep for as long as they can hold their breath - 20 or 30
minutes. (Humans and other land mammals are involuntary breathers - so they
keep breathing while they sleep whether it's for a night or an entire
winter.)

When you think about an animal who is able to maintain half of their brain activity so as to be able to breath and keep an eye out for dangers whilst resting the other half, it's pretty amazing. I have heard of whales sleeping in groups with the outer whales taking "guard" while the inner whales in the pod can rest easy. Then they exchange positions and share the sleep time.

Look forward to watching Humpbacks in the coming months as they migrate past the Gold Coast towards the sub-tropical waters for breeding and birthing.  We may find some of the whales sleep this season on the Gold Coast

For more information regarding Humpback Whales Sleep try this link to Wikipedia.