Ribeira de Aljezur, also known as Ribeira da Cerca spawns in serra de Monchique which is a beautiful place to visit by the way, and flows into the Atlantic in praia da Amoreira in Aljezur.
This river is around 18km long, inaccessible by boat, possible with stand up paddle (SUP) in some parts though. It's a beautiful ecosssytem where you can find a great variety of wild life such as otters, grey-heron, common-kingfisher among many other animals and plants!
Amoreira beach has an excelent water quality, tarmac access, it's around 200m long, produces good waves for surfing. Many fishes can be targeted such as Seabass, Mullet, Seabream among others.