Researchers were in a remote region of the Bellingshausen Sea on a different expedition when the iceberg calved, giving them a chance to change course and explore a region never before accessible to humans.

A gigantic iceberg cracked off Antarctica on Jan. 13, revealing a swath of ocean that had not seen daylight in decades. Researchers decided to search the seafloor under the freshly exposed ocean. What the team members found surprised them: giant sea spiders,