Kayak
At ria de aveiro or rio vouga - it is quite easy to find local guides that takes you for a different afternoon experience.
Surf
praia barra
At costa nova and barra beach - you can rent a suite and a bord on local surf shops.
Windsurf and Kytesurf
On the river and on the sea - you can rent this material on local windsurf shops.
tours
Moliceiro tours - leaving from the central canal.
Take some sun
At costa nova and barra beach
Walking tours
There is a local walking tour shop that has 3 way-outs every day.
Sailing
At costa nova beach - there's a local sailing club - cvcn - where you an find sailing lessons.