Report about an incident involving a group of school children kayaking recently published by the Marine Casualty Investigation Board of the Republic of Ireland.
The group were using a centre without external accreditation, their instructor had no formal qualifications, a gale warning in force on the day appeared not to have been heeded, access to a support boat may have helped resolve the situation more quickly.
All seven pupils and their instructor capsized and ended up in the sea in rough conditions. Fortunately, all were rescued successfully with no fatalities or injuries. Download the report from here.
You should only use adventure activity providers which hold up to date, credible, external accreditation for their activities.