Whitey Bay

Whitey Bay is a New World pirate captain known as the Ice Witch. She is one of the many pirates allied with Whitebeard who have journeyed to Marineford to rescue Ace.
She commands a ship that is an icebreaker. It is capable of going through ice covered waters.
Upon learning that Ace was going to executed, Whitey Bay and her crew joined forces with several other pirates and Whitebeard's crew to rescue Ace. Arriving at Marineford, as the war with the Marines began, the pirate alliance found their ships frozen at sea by Aokiji. This setback however didn't stop Whitey Bay and her crew. Due to their ship being an icebreaker, they simply broke through the ice. As they sailed, they created another opening in the Marine's formations for which Whitebeard and his allies could progress through aside the opening created by Oars Jr. earlier.

Source: