From The Human Clans
The people of Shark Clan are warriors and sailors that dwell in the seas of the Qi Province. They are also rogues -- pirates, that make their living by attacking other ships and stealing their goods. Little is known of Shark Clan, for historians are not exactly welcome among them. All I can say is that if you sail upon the Reshal Sea and are approached by a ship with a shark's flag, you would do well to pray to Lemicus for safety.
From Historian Zelka, building upon the work of Zuebara Pulan in the book The Human Clans
Until recently, little was known of Shark Clan by outsiders save for whispered rumors, snatches of old, moldering texts, and, of course, the rampant piracy.
Over the last several years, however, I have worked hard to build trust with people in Shark Clan in order to gain access to their stories and ways, with an aim to not only understand them and their history better myself, but perhaps to also bring this to the rest of the world so that the relationships between this insular Clan and others may be built upon truth and understanding going forward.
In my time with the Clan, I have come to understand that to say that people of Shark Clan are warriors, sailors, and pirates that dwell in the seas of the Qi Province is an understatement of great proportions. Their traditions are often predatory in nature, just like their namesake, but beyond that they are also protectors, innovators, and people who see themselves as a pure, untainted extension of the sea itself.
The shark moves forward, and the same can be said for this Clan. Originating from a band of early seafaring Humans, Shark Clan is deeply religious. They see themselves as part of the ocean, having adapted their lifestyles to existing nearly entirely aboard ships at all times. Shark Clan sees that all of them are born in blood and salt water, and so too do they all live in it. This attunement to the more brutal aspects of nature, and particularly the sea, has left the Clan with little moral compunction against piracy or raiding. They see it as a form of hunting no different than any other. It has, however, also lead them to a sense of morality in that they 'hunt' no more than they need to survive, just like any shark. Their raids and pillaging expeditions are never to become rich, but instead a simple extension of what they are as creatures. In truth, Shark Clan roams the entirety of the oceans, not just those nearest Qi, though different families tend to remain within the same set 'territory', and thus the acts of active piracy vary depending on the needs of the families in any given area of the ocean.
Their reputation with outsiders is complicated by the fact that many Shark Clan members have also participated in the activities of The Red Sash Pirates, but Clan elders and traditionalists frown upon this practice, seeing it as an affront to their place in the ocean's life cycle. However, the core of the Clan does not engage in such activities, instead keeping to their own ships, and their own form of worship. Shark Clan members are, incidentally, just as likely to be followers of Eluned or Lemicus as they are of Drogor, and all give at least some fealty to all three Aspects.
Though only tangentially related to the topic at hand, it is important to note that there exists a prominent offshoot of Shark Clan that lives on the difficult to reach island of Tref Bain. This group split with the Clan proper long ago, but the two groups hold no ill will towards each other, instead seeing themselves as close cousins. This island group is not recognized as a formal Human Clan, but their close blood and cultural ties to Shark Clan are evident in their protective natures. It is my great hope that I will soon be honored with permission to travel to Tref Bain and meet with these people. 
Shark Clan is widely conflated with the Red Sash Pirates (who are also known as just 'the Red Sash') by outsiders, but this is not really correct. While some Shark Clan members do join in with the activities of the Red Sash Priates, the Red Sash is an entirely distinct group from the Clan.
The Red Sash is a group of pirates operating in the Reshal Sea. Historically composed of and led by humans, it is presently led by Aedem, an elf, in the aftermath of the death of Sallador, a human. Aedem had joined the pirate group shortly before becoming its leader, previously being known as an independent operator.
The group had (ca. 2002) been dormant and thought dispersed before a series of attacks that eventually culminated in wide-ranging attacks during the Outcast War.
Long ago, the group was just known as the Sashes, and was a small Human organization (not quite large or formal enough to be considered a true Human Clan) like many others, though preferring to roam the seas rather than stay on land. Group members wore sashes to distinguish themselves by rank and position. Leaders wore purple; warriors, red; and merchants and other wore other colors, such as yellow, blue and green. It is believed that their society fractured in some way, as red sashes predominate greatly nowadays. 
- GM Persida on the forums, 4/13/18
- GM Jaedren on the forums, 7/6/2011, and GM Persida on the forums, 4/13/18