There is an excellent concrete slipway two hundred metres up river of the Tees Barrage. It has really good vehicle access with loads of room to manoeuvre a towed trailer. There is also plenty of free parking space. The well-maintained slipway has a pontoon along its full length, which then turns to continue along the wharf (Handy for temporary mooring and loading). The whole area is secured with locked gates between 2100 and 0600hrs.
The slipway gives access to 18 miles of navigable river upstream - with some rather delightful scenery once you get through the residential area. With plenty of mooring points, there are shops, fast food outlets and pubs within very easy walking distance, both at Stockton-On-Tees and Yarm. The speed limit is restricted to 5mph, apart from an allocated and marked mid-stream area given over to jet ski use at specific times, near the Barrage.
A River & Canal Trust (RCT) day ticket can be bought for £7, but if you are a regular user, I definitely recommend the flexible 30 day 'Explorer' ticket which can be purchased online from the RCT website for £108 and is valid for one year.
With a marine VHF radio, you can contact the Barrage office, who will open the automated lock and provide access to the tidal river downstream to the Tees estuary. However, you must also radio the river authority for permission to pass through their controlled and often busy industrial waters.