The phenomenon was observed in along the Algarve coast, and the Cascais and Ribeira das Naus waterfront, in Lisbon.

The National Maritime Authority said it is a “natural and common” occurrence at this time of year, resulting from “the combination of the equinoctial tides (the biggest of the year) with an accumulation of oceanic bodies close to the coast due to wind and strong sea agitation from the southwest”.