Sea Dogs are a group of seafaring pirates who are part of the Snow Pirate Elites faction. They wear heavy scuba gear resembling an old diving suit. They have apparently allied themselves with Nevec and are seen guarding many of Nevec's bases.
Sea dog mean an old, and experienced sailor or a lower rank officer in navy. Sea-dog also may referred to the real life piracy in 1560-1605.
The suits also bear a strong resemblance to the suits in the 1954 "20,000 Leagues Under the Sea", specifically the "crown top" helmet design, oxygen tanks and the emergency oxygen bottle on the torso.