I’ve found a simple pattern for a beginner like me.
So this year my kids are two little fish, one blue and the other one yellow!
I drew only 3 parts to create this pattern: a simple shirt pattern from a tshirt of my son, the tail of the fish and the gills. You can add more particulars to create a cute dress (some fins or an iridescent lining for example). if you have time do it!