This website is written for canoe, kayak and sit-on-top paddlers of all types; I've written it mostly, but not entirely, from my first hand experience of kayaking, surfing and walking throughout the county.
'Where to Paddle' gives specific information about the suitability of different waters for different levels of ability and different types of canoes and kayaks. I am not attempting a detailed geography, nor a guide to the wildlife of Cornwalls waters. These can easily be found by carefully searching the web yourself, though some of the best and most relevant sites I have discovered are listed on the links page.
The Cornish coast is 300 miles long with 300 beaches and a myriad of sea cliffs and headlands, half of it on the rugged north coast exposed to the Atlantic Ocean and the other half facing south onto the generally more sheltered English Channel. The whole encompasses many small but sheltered landing sites, over a dozen harbours plus all those harbours, small and large, in the 7 major river estuaries. Inland there are a number of small but paddleable rivers as well as our major river the Tamar which divides Cornwall from Devon and the rest of England. Cornwalls 'lakes' are mostly man made reservoirs as is the short section of canal at Bude.
All in all the paddling down here is fantastic, especially the sea kayaking, and has something for absolutely everyone except full-on whitewater kayaking; and even then you only have to cross to Dartmoor.
The Isles of Scilly aren't covered at present.