Sea surface temperatures around the UK have been the warmest start to the year on record, driving unusual species like bluefin tuna, octopus and mauve stinger jellyfish into British and Irish waters. Irish waters have cooled since a May marine heatwave but remain above average in the east and south.

"Temperatures in Britain will soar to nearly 21C later this week despite parts of the country having seen lows of -7C since the Easter bank holiday heat wave."

Scientists say water temperatures are as much as 3 to 4C above the average for this time of year in some areas.