Field Guide:
Merfolk

An extremely rarely encountered creature that lives in the open seas and oceans. Merfolk have the upper bodies of humans but starting at the pelvis, a tail and dorsal fin resembling those of cetaceans. Merfolk have webbed hands and sheaths of skin along their arms which aid in swimming. Although obviously a mammal, merfolk also have gill-like respiratory organs. These "gills" are attached directly to the lungs to supplement the creature's inadequate nasal passages.

The Fantasy Field Guide series includes these illustrations:

Strathmore 11 x 17 300 Series Bristol Smooth
Pentel CLiCK 0.5 PD275 MEXICO 9G Mechanical Pencil