KLM have just adopted new rules for dive equipment.
Formerly divers got a free 20kg extra and a maximum weight of a bag was increased to 32kg. Under the new rules you have to ensure no bag weighs more than 20kg and if you can't get your dive kit and your clothes into the standard passenger 20kg allowance, then the dive kit is charged 150 Euro.
See:
Excess baggage sportsequipment
The cheap airlines, such as Globspan and Zoom, now seem to outperform the full rate airlines on all counts. Zoom allows unlimited weight of dive kit.
Alex