are there boat tours in Porto in October? Are there trains to travel from Santiago de Compostela to Porto?
https://www.rome2rio.com/s/Santiago-de-Compostela/Porto gives you all the ways to travel
https://www.tripadvisor.com/Attraction_Review-g189180-d1549777-Reviews-Douro_River_Cruises_Day_Cruiuse-Porto_Porto_District_Northern_Portugal.html is just one river tour