Two Swansea University academics have been tracking jellyfish with GPS equipment.
They are trying to explain how the creatures are able to form blooms including hundreds to millions of individuals for periods up to several months.
Biosciences Professor Graeme Hays says jellyfish might look like mere drifters, but some of them have a remarkable ability to detect the direction of ocean currents and to swim strongly against them.
Professor Hays along with his Swansea University colleague Dr Sabrina Fossette tracked the movements of the jellyfish with GPS loggers and used GPS-tracked floats to record the current flows. They also directly observed the swimming direction of large numbers of jellyfish at the surface of the ocean.
They say understanding the distribution of jellyfish in the open ocean may be practically useful for predicting and avoiding troublesome jellyfish blooms, especially if it turns out that the findings in barrel-jellyfish apply to other species.
While jellyfish do play an important role in ocean ecosystems as prey for leatherback sea turtles and other animals they can also clog fishing nets and sting beachgoers.