They can appear fully human (albeit with shark-like features such as large and crooked teeth), as a normal shark, or in a hybrid form in which they have the head of a shark and the body of a powerfully muscled humanoid with clawed hands and talons on their feet.1
Weresharks believe that sharks have the right to rule over the sea, believe that they deserve magic items due to this right, and often recruit sharks to enforce their will within their oceanic dominions. A few weresharks rise to the leadership of island settlements. Some are bloody tyrants who sow fear among their subjects, while others are fair, distant overlords; regardless, most weresharks are single-minded and do not tolerate questioning. Weresharks prefer to give space to others of their kind and rarely fight, but when they do, the ensuing battle often leaves both scarred or dead. Chieftains and shamans of island-dwelling tribes often idolise weresharks.2
For additional as-yet unincorporated sources about this subject, see the Meta page.