Quick and Easy XP
In the icy part of the map you’ll find a sperm whale. Kill it and eat its remains. After the body has been gibbed, another whale will spawn INSTANTLY. Kill it, Eat it, Repeat. I said late game because it is a mini boss of sorts, meaning it has a fairly large amount of health and hits like a truck (unless your using a boss fish), it does around 800 damage.
This ice pillar and platform serve as my way-point.
Repeat this process until you reach around 582 devour size. from this point you can just devour the thing whole.
Eventually you become so large you can find a spot where you can just hold the eat button and instantly devour them as soon as they spawn. They have about 5 different places where they appear, all of them being close to one another.