For this mini whale, I used a grey chunky yarn and a 6mm hook. Since it was my first time making a whale, it took about 20-30 mins, but it should normally take only 10-20 mins, so it's a quick, fun, easy project.
This is the grey chunky yarn I used, which I bought at hobbycraft:
You can use any colour or type yarn, but I find that it is easier to use chunky yarn or plush yarn, but it is also ok to use acrylic yarn.
For the eyes, I coloured 2 black spots with a black pen, but you can use safety eyes or a black yarn.
This is the video tutorial that I followed:
This is not the only tutorial you will find, but it is the one that worked best for me. There is also a left handed version of this video available on youtube.
Trust the process, and don't give up! Have fun making this!