It is not yet known whet-her the three Britons – a couple and a female friend – are resident in Portugal or visitors.
RTP news reported on Thursday morning that the couple is understood to have lost all of their belongings in the incident.
One of the women was taken to Faro Hospital with signs of hypothermia.
The vessel remained underwater for a while after its sinking and was flagged with yellow warning buoys to alert other boats sailing in the area.