Look out over the ocean and you might get the impression that it’s a mass of water acting as a single entity. However, the world’s oceans are made up of layers of different densities, called stratifications, with complex fluid dynamics. Often bulges, called mode-2 internal waves, form in the thickness of these layers, trapping materials inside that then move along with the wave. For the first time, two mathematicians at Canada’s University of Waterloo have created a 3-D simulation of the mass transport capabilities of mode-2 waves. Such models will help define how mode-2 waves can carry materials that are either beneficial (such as phytoplankton and other food sources) or detrimental (such as crude oil and other contaminants) between ecosystems.