Stormwind Elite Aquatic and Land Forces

Stormwind Elite Aquatic and Land Forces, or Stormwind Seals, is a special detachment of elite soldiers trained and equipped to explore and fight beneath the sea. They were sent to Vashj'ir, not only to contend with the Horde, but to investigate the massive geological disturbances originating from the nearby sea floor.

Speculation
They may also be human marines.