You'll find a very 'fishy' knitting jumper pattern at Petite Purls knitting and crochet children's website. A brilliant pullover knitting pattern for all kids who love the water and everything that swims within. It's called "Beach Baby" by Christine H.Wilkins, sizes 0-6 years with the link below for the free fish pullover knitting pattern.

A crochet fish hat pattern by Jessica Flowers, too.
The sweater and hat set will be the favorite of little girls and boys who love the beach and the water world of worms, bugs, and deep sea creatures. These fishy hat patterns can be knit and/or crocheted in cotton for the spring and summer, or soft wool for cooler Vermont-like climes.
Beach Baby Stranded Colorwork fish sweater pattern for boys or girls.
The 'scarfish' fish scarf knitting pattern and 'half a fish' hat knitting pattern are both new free patterns. Original 'deadfish' fish hat patterns are available in English, Dutch, Finnish, Norwegian, French, Spanish, German and Portuguese.