Argo is an international underwater research program to monitor the oceans’ temperature, salinity, currents and bio-optical properties.
Operating since the early 2000s as a collaborative partnership of more than 30 countries from all continents, almost 4000 drifting ‘Argofloats’ have now been deployed worldwide and colour-coded by the country owning the float:-
Drifting at a 'parking depth’ of 1000 metres, the velocity of currents is calculated from the distance and direction a float drifts. Programmed to change buoyancy every 10 days, the floats dive to a depth of 2000 metres and then move up to the surface whilst measuring conductivity, temperature and pressure to calculate the oceans’ salinity and density.
Data, on surfacing, is then transmitted ashore via satellite and is freely available to everyone without restriction.
Best not bump into one!