They were an aquatic and amphibious humanoid race, characterized by large fins on their heads and back as well as large, webbed flipper-like hands and feet.
The Dai-ai were a private people and not particularly talkative. They desired only limited interaction with humans. However, when they did make contact with outsiders, they were pleasant and courteous.
Nevertheless, after months of negotiation, the Dai-ai made an agreement with the Federation to allow the Starfleet Corps of Engineers to conduct mining operations on Naia VII, which were underway by 2368. Starfleet gained raw materials vital to its defense while, in exchange, the Dai-ai were amply compensated with food and supplies. However, they had firm environmental regulations that disallowed particle beam– and transporter-based mining technologies, necessitating traditional and dangerous excavation methods. The Dai-ai had no interest in participating or endangering their own lives for the "unusual rocks". (TNG - Assimilation² comic: "Issue 2")