Loch Awe is going to be still pretty cold at this time of year , you would be lucky to survive 15 minutes , lifejacket or not. From what I've read the guys are regular visitors to the Loch apparently they normally take the boat across to the pub and some of the locals usually drive them back round the Loch to their campsite, unfortunately not this time.
How bad must have it have been for the 5th member of the party who could hear the cries for help but could do nothing because of the fog.
Its a bizarre fact but fishing is the most dangerous sport/ passtime in the UK , mainly due to the number of sea anglers who are washed off the rocks and drown each year , In this sad case it just emphasises the point that fishing and drinking do not mix.
Regards
Jim