What is Canyoning and Coasteering? Well I don't claim to be an expert, but they both seem very similar sports to me (please use the comments box below if I have got this wrong!).
Coasteering is a fun way of working ones away along a section of coastline jumping into the surf from the cliffs, and clambering up and down between the cliffs and the sea, whilst enjoying the sights, sounds and smells of dramatic coastal areas.
Canyoning is a similar sport but based inland on rivers. Due to the nature of rivers (which tend to flow down rather than up), Canyoning generally involves working your way down a stretch of river, swimming with the current, jumping into the river from dramatic waterfalls, entering canyons, etc on route, Again while enjoying the scenery, wildlife, sights and sounds of the river as you pass down.
Looking at the photos on YouGoDo for both activities, fun and thrills seems high up on the list of priorities for both sports.
Here's a selection of links;
Coasteering in the UK - it's particularly popular here - must be warm seas around the UK ;-)
Helmets and wetsuits on - Have fun!