In just one gulp of seawater, there are roughly 200 million viruses. But before canceling your seaside vacation, consider this: These viruses have their sights set on the ocean’s microorganisms, such as plankton. Scientists got an unprecedented look at the viruses swirling around the upper ocean as a result of the Tara Oceans expedition. From 2009 to 2013, scientists sampled 26 sites across the world’s oceans. Jennifer Brum and Matthew Sullivan, from the University of Arizona, are among the researchers studying these samples to catalog and understand the viruses that influence the ocean’s—and by extension, the world’s—ecosystem. Their results were published in the journal Science this week.

*This text was updated on March 26, 2015, to reflect the following change: An earlier version stated that, from 2009 to 2013, scientists sampled viruses from 43 sites across the world’s oceans. In fact, they sampled them from 26 sites.