The Waimea River Walkway goes from the Tomlinson Picnic Area at the western end of the Wai-iti River bridge in Waimea West Road (S41 21.963 E173 05.922) to River Road (S41 18.986 E 173 07.356). You can also enter at the end of Livingston Road (S41 21.672 E173 06.148) but if there is lots going on in the vineyard you might choose not to park there. There are no other entry points so unless you know people whose property borders the walkway you will need to use one of these points.
You can walk or cycle the length of the walkway. It's mostly along the top of the stopbank, so virtually flat. One word of warning though, it's not particularly well maintained so you'll find yourself brushing past paspalum seeds and having to look at convolvulus, old man's beard, gorse - - - you name it! Having said that, you don't have to push your way past prickles or anything like that so it's not all bad.
This series of caches has been placed along the walkway. They're all puzzles - - the instructions for finding the first one are shown on the cache page. Each of the log books for caches 1 to 4 have instructions for finding the next cache.
You will need to bring your own pen or pencil. Some of the caches have pencils in them, most do not. You might also find a piece of paper useful.
Enjoy!