Simplify the following text for a Grade 15 native English-speaking person.
Original: An alternative plan was devised in the 1970s to extend the Jubilee line parallel to the River Thames : this would have taken the line from Fenchurch Street to Thamesmead via St Katharine Docks , Wapping , Surrey Docks North , Millwall ( near to South Quay Docklands Light Railway station , North Greenwich , Custom House , Silvertown , Woolwich Arsenal , thence to Thamesmead .
Simplified: An alternative plan was created in the late 1970s to extend the Jubilee Line in parallel with the River Thames , this would taken the Line from Wapping to Thamesmead Via Surrey Docks North , Canary Wharf , North Greenwich , Custom House , Silvertown , Woolwich Arsenal and to Thamesmead .