Mermen have a long history and appear in the mythical stories of many lands, including Greece and the Nordic countries. Mermaids, the mermen's female counterparts, are more common in art and folklore, but you may prefer to draw this more obscure underwater creature. Mermen have been portrayed in different ways. Some are handsome and strong while others are ugly and monstrous. What kind of merman you'd like you draw is entirely up to you.
Sketch the merman in simple shapes first. Start with an oval shape for the head. Then draw a rectangular shape from the bottom of the head down for the neck. For the torso, use a big rectangular shape. Make sure to make the top of the torso shape wider than the bottom. Create arms by drawing two cylinders. Taper the cylinders near their ends, where the hands will connect. Hands can be kept as simple ovals.
Draw the merman's tail. This part of the drawing shouldn't be as precise as the human part of merman. The tail can be more freely formed with curvy lines to portray movement, but should still basically be the shape of an elongated, upside down triangle, starting at the merman's hips. Look at a picture of a fish as you are drawing the merman's tail. The top part of his tail should be as wide as his hips and then gradually taper to a narrow point at the bottom. Draw the tail to match the proportions of the merman's torso; it should be approximately as long --- or a little longer --- as his legs would be, if you were to draw him with legs.
Draw the tail fin and scales. The tail fin should be triangular in shape, with the top of this triangle extending out from the bottom of the tail and flaring out wider at the bottom. Both sides of the tail fin should be symmetrical. If you'd like to create additional fins, you may add these wherever you'd like. Scales can be created by drawing rows of adjoining "C" shapes along the main part of the tail. The scales can point in any direction you choose, but keep the direction consistent. Draw the scales fairly small, as a fish's skin is lined with hundreds of tiny scales. Add vertical lines to each fin to create texture, starting from the top of the fin. Space the lines fairly close together.
Finish the details of the human part of the merman by connecting the shapes together and smoothing out the lines. Draw in the face. Using your reference picture of a man, draw in the eyes, nose and mouth. You can create any hairstyle you'd like, but remember that in the water, longer hair will look like it's floating. Hands can be difficult to draw, so keep them simple and draw, very lightly, one shape for the palm and very light lines for fingers. Then draw the finger shapes around the simple lines and connect them to the first simple hand shape. Connect the hands to the arms. You can erase the original light lines within the hands. Feel free to add more detail, such as decorative seashells, seaweed necklaces or other marine embellishments.
The more you draw mermen the better they will be. Don't expect your first attempt to be perfect.