Here is an alternative guide to grades.

class I - "... Risk to swimmers is slight; self-rescue is easy."
Take the Mother-in-law

class II - "... Swimers are seldom injured and group assistance, while
helpful, is seldom needed. ..."
Take the Girlfriend

class III - "... Injuries while swimming are rare; self-rescue is usually
easy but group assistance may be required to avoid long swims. ..."
Take the Wife

class IV - "... Risk of injury to swimmers is moderate to high, and water
conditions may make self-rescue difficult. group assistance for rescue is
often essential but requires practiced skills. ..."
Take the Mistress

class V - "... swims are dangerous, and rescue is often difficult even for
experts. ..."
Take the Photographs

class VI - " ... The consequences of errors are very severe and rescue may
be impossible. ..."
Take the Mother-in-law

--
Dave Manby
Details of the Coruh river and my book "Many Rivers To Run" at
http://www.dmanby.demon.co.uk