There's a little more to this cache than meets the eye.
If you go to the coordinates, with a torch and look DOWN - you should be able to see the cache.
Now what?
Welcome to the delights of the Beck Valley Storm Water Culvert, which runs nearly two miles across this side of the city into the Trent at the end of Trent Lane. You only need to navigate for the first 200m. Walk to the end of Trent Lane and read the plaque. Look over the edge - you are right above the entrance.
You have two options - boat - definitely the most sensible. The parking and launch coordinates are one way of doing it.
Or - like the FTFer - you can climb over the wall and wade in - but it could be 2 to 3 feet deep.
Up to you - have fun! But please stay safe.
For more about this fascinating place - here are two web links.
https://substormflow.com/drain/beck-valley/
https://www.28dayslater.co.uk/threads/beck-valley-storm-water-culvert-nottingham-september-2016.105400/