Taking underwater macro photography with freedive is more difficult than some people think and criticize.
First of all, you have to learn to keep your breath and equalize right your ears, especially if you go deep. Then you have to stay still with currents (and sometimes strong currents) and focus your camera on the species you want to take a photo.
On this poster, you can see a nudibranch species (Cratena peregrina) which doesn't grow over 5 cm. But on those photos are about 1 cm only. And on the right circle, it's their food, which is some millimeters in size.
Now, for those who think it's easy, why don't you go out and take similar photos (if you can)?