Make your dog look like the most feared creature near the water bowl! Find a t-shirt that fits your dog, remove the sleeves and cut out a large half-oval from the stomach area. Cut triangles of felt to make the fins and tail, sew or glue the edges of the triangles together and put triangles of cardboard into each pocket of felt. Attach the fins along the back and sides of the costume, and attach the tail at the base of the costume. Stretch one of the t-shirt sleeves, cut a slit in the back edge of the sleeve if needed and cut out ear holes from the top of the sleeve. Cut a triangle of grey felt, attach small triangles of white felt across the top edges of the grey triangle and attach the base of the grey triangle along the top edge of the t-shirt sleeve.