Poole Harbour is shallow, sheltered and very large, which is close to ideal for learning anything that floats. It is also a working harbour with ferries, commercial traffic and a strong tidal flow at the entrance, so the rules matter.
Learning
Sailing schools and clubs around the harbour run RYA courses from dinghies up. Windsurfing and paddleboarding tuition is widely available, and the flat water means a first lesson usually ends with you standing up rather than swimming.
On your own board
Launch points are spread around the shore, with the harbour-facing beaches the easiest. Stay out of the main channel, give the chain ferry a wide berth, and read the wind: an offshore breeze across a shallow harbour will take a paddleboard a long way before you notice.
Kitesurfing and windsurfing
The combination of shallow water and clean wind has made the harbour a serious windsurfing venue. Conditions vary sharply with the tide, so local advice is worth having before your first session.
See also boat tours if you would rather be a passenger, and the harbour guide for tides, navigation and wildlife.