Diving the Unknown:
Cave Diving in the Riwaka Caves, Nelson
by Bruce Walton
A dive into the source of the Riwaka River is a real adrenalin-pumping experience, a dive that once undertaken will give you a sense of achievement. Situated at the foot of the Takaka Hill, beneath a black, watery hole, hidden and almost unknown to most who visit, lies a fantastic underground network of caverns.
The source is only 68km from Nelson, and is reached after a pleasant drive through some of New Zealandâs major apple and hop producing areas. Crafts, potteries and many other distractions are passed before you reach the turnoff. Insignificant compared to what you have seen, it is easily missed â so donât climb the hill! A variety of accommodation is available along the route, with well-known Kaiteriteri Beach only 40 minutes away. You and your party may decide to make a weekend of it. Many do, as there is plenty to do and see for everyone.
As you follow the Riwaka River, the road passes through farmland before slowly giving way to regenerating bush and finally entering the WF Moss Reserve, an area of beautiful native bush; the end of the tarsealed road. From here itâs only a short distance along a winding and narrow stretch before arriving at the Riwaka Resurgence Scenic Reserve. A large well-kept grassed area with toilets, tables and shade makes an ideal place for your party to picnic and set up. Fantails, finches, waxeyes and many other birds will join you. Gathering amongst the trees, they feast on the many insects and berries around.
The cool freshwater stream contains crayfish as well as safe swimming holes: a peaceful escape from city life, and a very popular picnic spot. Native bush surrounds the river and track up to the source. Ferns and mosses of many species carpet the forest floor while rimu, totara and other native trees form a canopy above. Lichen-covered branches create an eerie feeling of mystery belonging to the forgotten past. Photographers or botanists could spend all day here, but there is diving to be done.
The track is easy; the last part, to the information platform and Crystal Pool Lookout, has steps. Try taking in your heavy gear first, then return to suit up and make final plans. Takaka Hill rises 600 metres above. These sheer rock faces contain a network of cracks and caves, with the Riwaka Resurgence possibly being the most accessible. Covered in mosses and surrounded by dense native bush, you are hemmed in. The only exit is the track and the endless flowing river. Your dive is much the same: your entrance is your only exit! Safe, correct cave diving procedures should be followed. Commercial operators are not permitted to operate trips here, which is possibly the reason no permanent guidelines are in place. Local dive clubs do regular trips, and dive shops in Nelson will arrange your diving needs.
After climbing down the wooden steps to the rocks below, you are able to do your final gear up and check. There is enough room for setting up. It is a good idea for the first pair to take the guideline in, tie it off and then return for the rest of your group, which keeps everyone in the party together. Follow the basic rule of thirds for air, and take two torches plus safety lines. I have found small cyalume sticks on your tank a great idea.
The source itself is a formidable sight. The hole is only four to 12 metres deep, and the water temperature is more appropriate for polar bears! However, the buzz you get will be reward enough. While the water is usually clear, the entrance disappears into absolute inky blackness. Divers react in many different ways to cave diving. Caves make exceptional demands on a diver, physically and mentally, and those who dive into this unknown world will respond in many different ways. Buddy awareness should be top of your list.
A short distance into the source, you will be able to surface into fresh, cool, pure air; but with a sharp right hand corner, current and possibly rapids, it is best to have your lines well tied. A large rock just before the rapids helps. There are numerous passageways and caverns here with fantastic formations, and many parties only go this far. Use a line from your site inside, in spite of it being above water level.
The Greenlink is only one cave system that drains the Takaka Hill into the Riwaka, and has only been dye traced. This system has been dived since the early â60s, and there have been various expeditions by very experienced and trained people; however, the system is still being explored. Up until recently, little was known beyond the third lake, but now people have pushed on much further and discovered a number of unique formations. Climbing over a small rock fall you will find the next lake, ten to 12 metres deep and over 45 metres long. It is the largest and deepest found so far. A rock overhang forces divers down, but heralds the entrance to a large lake and our next stop. The Cathedral, so named because of the high roof as well as the rock pile that climbs up to the next level, is a massive area. Many small corridors and passages lead from this chamber.
The marble rock was once tiny marine animal skeletons, deposited onto an ancient sea floor and cemented together into limestone before their further transformation into marble 500 million years ago. Now uplifted to its present position, water dissolved this faulted rock, creating distinctive underground and surface features. Water droplets pausing on the roof redeposited the dissolved minerals to create a diversity of colours and shapes over thousands of years. Stalactites on the ceilings joined stalagmites on the floor, creating giant pillars. Others are so close to joining that the naked eye finds it hard to see. Many others have ice or crystal-like appearances, while some give monster impersonations from long-lost Walt Disney features â these are only limited to your imagination!
Leaving all unwanted gear at the base of the awesome rockfall at the end of the lake in The Cathedral is quite safe, but a cyalume stick does help in finding it again. You will not need dive gear for any of the further lakes so far discovered, and it does make the climb much easier. Many side passages lead off in different directions. Although they too have interesting formations, many are dead ends. The next two smaller lakes can be swum with little trouble, before climbing up a waterfall to the last of the chambers that have been fully explored. You will need planning, equipment and experience if you wish to push further.
The formations here give photographers plenty of scope for really creative image making: juggling a torch between your knees while trying to focus adds a new and challenging dimension to photography. Please remember one thing in the Riwaka Resurgence. The water you see has travelled more than four kilometres underground, fallen 600 metres and taken three days to get here. Delicate formations have taken thousands of years to grow only a few millimetres … and they can be destroyed in a fraction of that time. A carelessly placed foot or elbow can wipe out centuries of nature. Any damage you find here can only have been done by divers. Take only memories and photos, and leave only footprints, so future generations can also enjoy.
Returning to the outside world, shivering with cold, torches slowly dulling, consider how many think caving is a form of insanity. Or is it something else? You have been diving the unknown … only you will know the answer
There are numerous dive clubs within this area, and Christchurch clubs also do trips there. The Nelson, Motueka and Golden Bay clubs are three who do trips into this fantastic place; see the classified pages of this magazine for club contact details. Many dive shops will assist in setting up and organising the required specialists for this dive, but will not run trips, due to the non-issue of permits. This also applies to Te Waikoropupu (Pupu) Springs. These regulations have been brought in to protect this unique region. Unfortunately the Department of Conservation, who administer this area, have no written information available. Takaka is well known for its caves, sumps and underground networks, and is the easiest area to dive without special gear. For the Riwaka, it is best to have at least two long guide lines, the longer the better, but 100 metres and 50 metres minimum. There is a sign showing a plan of the system at the resurgence source. The New Zealand Diverâs Handbook (by Peter Rippon – now out of print) is also helpful if you can find a copy. The distance from Blenheim to the picnic area is 184 km, about the same distance as from Picton. Many have come by ferry to do this dive. Enjoy your dive to the unknown.