As for the Royal Military Canal. Lovely place to kayak on, but that won't be on your itinerary.
So if you want a little something to watch on YouTube before turning in for the night, you can learn all about it's history from this nice little three parter. Part one below:
If you go down Harbour Road and follow the footpath off by the lock then there's a lovely circular walk that'll take you down by the side of the River Brede and back round past Camber Castle. Don't be fooled, it's a short walk of just 3 or 4 miles all in and goes no where near Camber...