Tension and lack of practice render the beginning of the sea journey quite difficult. Crewmembers attempt to remove bigger pieces of ice floes crashing against the boat with poles, but the weight of the ice renders this futile. Nonetheless, the boats make progress and the ice pack appears to be looser. Killer whales and seabirds abound. Shackleton sets a course toward the northwest. Within a half hour, the men become aware of a “deep, hoarse noise that [is] rapidly getting louder” (178). The icy equivalent of a lava flow, two feet high, is approaching the boats. This is a tide rip, “a phenomenon of current thrown up from the ocean floor which [has] caught a mass of ice and [is] propelling it forward at about 3 knots” (179). Initially halted by shock, Shackleton orders all boats to row toward port. The rip continues for around 15 minutes. The boats have now reached the 200-mile-long Bransfield Strait, a treacherous body of water connecting the Drake Passage with the Weddell Sea. Very little is known about this area, although the US Navy describes it as setting up a “cross sea”: a condition where wind blows in one direction and the current in another.