Size is easy to adjust. Use 4mm G hook for Newborn, 4.5mm G Hook for 0-3 Months, and 5mm H hook for 3-6 months. The blue whales were made with a 4mm hook and the yellow ones were made with H.

You will need a small amount of #3 crochet thread and a size 0 steel hook 2 for the eyes. Or just use a lightweight black yarn,or very securely sewn buttons. Mouth in embroidered on with the crochet thread.