No tutorial, but could be done by just looking at it. Would be pretty out of crocheted snowflakes!
Vector snowflakes set by Rosinka, via Dreamstime
Summer Tic Tac Toe Cookies by Melissa Joy
Incredible under the sea cookies!
The Cookie Lab by Marta Torres A summer royal icing decorated cookie (lisi martin)
Girly Goldfish Cookies | Cookie Connection
Tropical Fish Cookie Cutter $5.00 http://www.fancyflours.com/product/Cookie-Cutter-Tropical-Fish/s
Fish Sugar Cookies. $19.95, via Etsy.