The two mermaids seem to be singing their enchanting melody and enjoying the peacefulness of their lagoon. The beautiful creatures have the head and torso of a woman and the tail of a fish, and are seated on rocks among the foamy waves. Beyond them, a majestic sailing ship is in the distance, silhouetted on the horizon. To bring even more life to the page, I would use shades of ocean blue combined with light buff and coral for the rocks and the sirens' skin tones, and rich navy for the sails of the ship. Adding a touch of sparkle can be done with some glitter pens or adding a little gold or silver to their details. Their hair can be made of different earthy shades like browns and oranges, which will add a pleasant contrast.