June 2012: The Joys of Navigation, Osezaki, Shizuoka, Japan

Saturday June 16th and Sunday June 17th 2012

All dives require a focus on safety, buoyancy, air, buddies and depth.  With poor visibility or currents to consider as well, the underwater environment really is THE place to get lost.   Of course there are no maps and divers are faced with a random terrain of rocks or coral gardens with nothing but blue as they stare ahead.  As training for my Advanced certification begins this summer, one important skill I need to learn is how to navigate.

Before that however, the first thing is to plan your dive.  Here are some things to consider:

  • Location – is it sandy, rocky or full of coral?  Are there wrecks or any small tunnels?
  • Water conditions – is there any current or poor visibility?
  • Divers’ navigational skill and level
  • Dive plan – are the divers planning to head north for 15-20mins, head west and go south?  Or will they move from point to point?  Is there anything in particular they want to see?
  • Map – draw a map on a slate or look at an actual one.  This helps the diver keep a mental picture of the site.  It’s also useful to mark the depths on various points, the entry point or location of the dive boat.   Plan a route.

Underwater compasses have a big lubber line (direction of travel line), a bezel (a movable ring full of numbers around the edge of the compass), a card (the white movable part that says N, S, E and W and full of numbers as well) and a window (a small one at the side of the compass to look through as you swim along).

With the help of some online information, here are some navigation techniques I found:  To navigate using the window, point the lubber line in the direction you want to go, and you will see a number in the window.  As long as the compass is level and the number stays there, you are going where you want.  Before a shore dive, point the compass in the direction you wish to ascend and remember the number in the window so when you are swimming back, you know you are going the right way if you see that particular number.

To navigate using the bezel, point the lubber line in the direction you want to go, and turn your bezel until the double triangle bit is right next to the N on the card.  As you swim, keep the compass flat and steady and make sure the lubber line is pointing towards your destination.  Then you should always see the N next to the double triangle. If not turn slightly until you do.  If the bezel is correctly placed, the number in the window will also be the same as the number at the end of the lubber line.

You and your buddy might decide to descend along an anchor line, and swim at 150 degrees (this number is called the heading) to reach a wreck.  Once you’re at the bottom, turn until you see 150 in the window, or turn your bezel so that 150 is at the far end of the lubber line and turn until the N is in the double triangle of the bezel.  To get back using the bezel, turn until the N is next to the single triangle.  Using the side window, note the number directly across from the direction you were heading in.  The number across from 150 is 330, so if you keep 330 in your window as you swim back, you should get back to that anchor line.

When navigating, it is easy to focus only on the compass and neglect your buddy and what is around you.  To make sure you keep an eye on your buddy and see a few things as well, look at the number in the window (for example 150), make a mental note and take in your surroundings.  It’s okay to swim a little to the left or right if you want to explore something or take photos.  Just remember that number 150 as you head to your destination.

My dive group train at Osezaki Bay in Shizuoka prefecture.  Located on the west side of the Izu Peninsula, the sheltered bay is C-shaped with a long beach full of dive schools, calm waters, a sandy bottom and plenty to see.  All of these make it very popular for dive training.  Further west of the bay are deeper areas full of boulders which you get to by loading up your dive gear on a cart, and heading out on foot.  The bay is particularly good for navigation as it is littered with objects – car tires, small statues, metal structures, a particularly huge concrete boulder, a motorbike, a boat, the list is endless.  Some are joined together by ropes, so to practice simple navigation, the best thing is to pick some objects you want to see and aim to reach them.

My buddy and I planned our dives using a map of the area complete with depth information.  For my first dive, we planned to head past a concrete boulder and follow a rope down to about 20m where we would find some car tires.  After exploring these we would ascend, stopping to look at a small shrine entrance before emerging at the surface.  With a picture of the map in my mind, I reached the car tires but got lost ascending and couldn’t find the shrine.   The deeper areas have no landmarks, so we discussed how deep we should go before turning left or right, and much air we should have when turning back.   I felt like more of a landmark person because I managed to pick out some rocks, whip coral and other features and successfully returned to our entry point, having remembered that we descended over a sandy slope that stood out among the rocks.  On Sunday, poor visibility at 20m completely threw me and I got quite lost but later things improved as I was more familiar with the site.   During the weekend we saw moray eels (including one being cleaned), blue banner fish, an incredible school of sardines (very rare to spot!), purple anemones, stone fish, wrasses, lion fish, sea urchins, catfish, nudibranchs and Moorish Idols.

Navigation sounds intimidating but it needn’t be.  Veering off course or finding something not part of the dive plan are opportunities to discover new sites or creatures, and trying to reach a destination is like a game and fun in itself.  It’s important to turn something that seems complicated into something that is fun, and with practice I’d like to learn more about the joys of navigation as well as the skill itself.

Practical information

  • To get to Osezaki, take the Shinkansen bullet train from either Tokyo or Shinagawa stations.  The early morning one leaves Shinagawa at around 7:34AM (destination Nagoya) and arrives at Mishima station around 8:19AM.  A one-way ticketwith no reservation costs 2,210yen.
  • It takes 12 mins to change trains at Mishima station.  Follow the signs to the Izu Hakone Tetsudo Line (Sunzu Line), destination Shuzenji.  The journey to Izu Nagaoka station is about 20mins and a one-way ticket is 320yen.  One train leaves at 8:31AM and arrives at 8:55AM.
  • At Izu Nagaoka station our dive shop accommodation (Osezaki Marine Service http://www.fuji.ne.jp/~osekan/)offer a pickup around 9:30AM.  It takes around 30mins to Osezaki Bay.
  • The dive shop is located right on the Bay with basic accommodation behind.  It has a big area selling books where people can leave bags, food and drink.  Outside are the tanks, while wetsuits, boots, masks etc for rental are behind the counter.  There are 3 toilets next door along with male showers.  Female showers are up some stairs into the building opposite.
  • Bring your own tea, coffee and snacks to have in between dives.  Hot water is available but cups must be borrowed from the restaurant next door.  Plenty of vending machines selling water, beer and soft drinks.
  • The shop takes a large area of the beach where customers can set up equipment.  You are responsible for everything – changing tanks, cleaning, and making sure everything is kept together.
  • To go to the deeper areas further west, take one of the carts parked nearby, load it with your equipment and head over on foot.
  • As I’d come with my group, there were no guides from the shop to accompany us on our dives, but no doubt this can be arranged for private bookings.
  • Lunch is available at the restaurant next door.  For around 1,000yen you can get basic curry, set meals of rice, miso soup and fish, or noodles.  Coffee is around 300yen.
  • All dives are shore dives, basic beach entry.
  • There are huge containers of water to wash wetsuits, BCs, regs, boots, masks and fins.  These can all be hanged on the rack next to the containers.  Compasses, dive computers, SMBs and cameras can be soaked in a smaller container next to the shop.
  • We stayed in basic accommodation next door to the shop.  One room can sleep at least 3-4 people on the floor.  All rooms are Japanese-style with tatami straw mats.  Dinner and breakfast not provided.  Our group usually has a BBQ.
  • There are no shops in the area so it’s a good idea to stock up on food and drink at the convenience stores close to Izu Nagaoka station.

June’s dives

Dive 1: Osezaki Bay: depth: 19.3m, dive time: 36mins, water temp: 22C, entry time: 11:42, exit time: 12:18, average depth 10.5m, used a 12L tank, 5kg weight belt, 5mm wetsuit and 2-3mm hood/vest, start pressure: 200 bar, end pressure: 65 bar, saw sea urchins, lion fish, moray eels, purple anemones, stone fish, scorpion fish and wrasses.

Dive 2: Sentan, The Point, Osezaki: depth: 21m, dive time: 41mins, water temp: 22C, entry time: 15:10, exit time: 15:51, average depth: 12.6m, used a 12L tank, 5kg weight belt, 5mm wetsuit and 2-3mm hood/vest, start pressure: 200bar, end pressure: 60 bar, saw moray eels, sardines and whip/soft coral.

Dive 3:  Osezaki Bay: depth: 22m, dive time: 34mins, water temp: 22C, entry time: 10:23, exit time: 10:57, average depth:12m, used a 12L tank, 5kg weight belt, 5mm wetsuit and 2-3mm hood/vest, start pressure: 200 bar, end pressure: 60 bar, saw a beautiful butterfly-like fish with wonderful big blue wings.

Dive 4:  Sentan, The Point, Osezaki: depth: 21.4m, dive time: 49mins, water temp: 22C, entry time: 13:08, exit time: 13:57, average depth: 12.2m, used a 12L tank, 5kg weight belt, 5mm wetsuit and 2-3mm hood/vest, start pressure: 200 bar, end pressure: 60 bar, saw nudibranchs, Moorish Idols, great colourful fish actually eating seaweed and the massive school of sardines once again.

About Rising Bubbles

Based in Bristol, UK, I am a freelance writer and consultant working on Japan’s aquaculture and fisheries development. My work focuses on issues related to sustainability, research, gender, technological advancements, adaptation and resilience. I have a keen interest in the recovery of aquaculture in the Tohoku region, following the Great East Japan Earthquake and Tsunami of March 11th, 2011, and provide news stories, features and reports from Japan for national and international seafood and fisheries media. While living in Tokyo between 2006 and 2017, I worked as a freelance writer on Japan’s aquaculture and marine-related subjects, in particular scuba diving. My blog began in 2011 as a comprehensive guide to diving in Japan. I have enjoyed exploring Japan’s waters extensively and became a certified Dive Master in August 2015. I hold an MSc in Sustainable Aquaculture from the University of St Andrews, and a BA in Japanese and French from the University of Cardiff, UK.
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