August 2012: Izu Ocean Park (IOP), Izu Kogen, Shizuoka, Japan

Wednesday August 15th 2012

Sandwiched between the Sea of Japan and the Pacific Ocean, Japan is a surprise in store for many divers.  The country’s main islands and smaller ones are scattered across the archipelago, making conditions ideal from ice flows up north to tropical waters down south.  As summer approaches, warm currents flow along the islands south of Tokyo while in winter a cold current brings icy waters south from the Arctic ocean.   All this means that divers can experience the crystal clear blue waters of Okinawa, the cold waters of Hokkaido, tropical coral reefs, kelp forests and even ice diving all in one year.

Since 2011 I’ve been coming across new dive sites in Japan and today visited another, Izu Ocean Park or more commonly known as IOP.  The park was one of the very first sites to be explored years ago around 1965 and is a 15-min bus ride away from the nearest station.  Situated in the middle of a beach, it’s dotted with swimming pools and ample facilities for scuba diving, while the palm trees create a nice warm summery atmosphere.

Our dive school Little Ritz picked us up from the station and drove us to their shop 5 mins away.  The shop is a place to prepare equipment, sign wavers and collect rental gear before being driven to Izu Ocean Park itself, around 15mins away by car.  In summer, crowds of divers flock to the area and today was no exception.   The main road into the park takes you past rows and rows of picnic tables, another huge dive school (IOP Diving Center), swimming pools containing sea water, a massive outdoor bath, shower, and changing room area with lockers, and a smaller building slightly further away with a freezer and ice available to store food and drink.  Although the area is busy, all facilities are easily accessible and there are nearby stalls selling noodles, ice cream and basic drinks.

Tanks are available at a separate area downhill from the picnic tables and near the entry point, so we walked down carrying all our equipment to set up by the water.  Izu Ocean Park has two main dive sites, the left beach and right beach.  The left beach is the most well-known for its diverse marine life and goes down to around 18m making it ideal for Open Water divers and beginners.  Angelfish, rock fish, lion fish and damsel fish are often spotted there.  For the more advanced, the right beach tapers down to between 28m and 32m.  A rocky area leads out to one underwater pinnacle with several nice forms of soft coral.  Having put on all gear, divers then follow a rope into the water wearing their mask and fins, forming a long queue as each enters the water one by one.  The sea can be very choppy and the rocks are slippery so it’s vital to hold onto the rope which remains until it is safe and comfortable enough to start swimming out.  A buoy further away acts as a good meeting point, and from there the descent takes you to about 4m, where plenty of rocks lie below.

The rocks are covered in seaweed and all sorts of life.  It is not tropical here by any means, but the waves and water movement can be fairly strong, washing away any sand and sediment and leaving excellent visibility.  Blue heavenly damsel fish, or neon damsel fish, swim over the rocks and in between the holes and cracks.  Half-lined cardinal fish, spotnape cardinal fish whitelined goat fish and scalpel sawtails are all known to live here.  Some rocks are tall, huge and almost boulder-like, providing ample space to swim around and look out for nudibranchs, small anemones, sea slugs, shrimps and crabs which can be easily found by shining a torch into the gaps.   Divers can get hidden away behind the rocks, and becoming separated from others can happen easily depending on how absorbed you are by the area, but the buoy is always something to look out for and a good marker by which to ascend if required.

The rocks remain over a considerable area, but as the water becomes deeper at around 8-10m, they suddenly turn into a considerable dropoff.  Here, visibility is a lot worse due to the sandy bottom, but all sorts of creatures thrive such as Christmas tree worms and camel shrimps at 12m.  Further down at 20m the area becomes sandy and from here it’s sand all the way to the dark depths.  With the rocks behind and slightly poor visibility, all there is is sand and one simple rope on which is a small postbox.  This is the highlight of the site.  The dive shop will laminate postcards which you can quite literally post, at 20m down.  Beyond the postbox is a medium-sized artificial cluster of plants which have been deliberately placed there for squid to lay their eggs.  Although it’s slightly late for this time of year (egg-laying season is around May), they are still being drawn to the warmer waters of the Izu Peninsula and we were able to sit and observe them from a distance.  The eggs are deposited onto the plant inside an egg case.  Many other squid lay in the same area, which is why eggs are often found in clusters.  They are usually laid only once as both the male and female will die soon after.

We took a slightly different route on the ascent over some more boulders and spent time exploring these.  Here the water tends to be rougher and controlling buoyancy on an emptier tank in such conditions is a bit more challenging but there is still plenty to see.  We came across an orange sea slug laying eggs, buried in a cluster of seaweed, and nudibranchs (Hypselodoris maritima and Ceratosoma trilobatum) holding fast to a rock.  During the ascent the rocks get bigger and spread out more, and visibility improves until you are back at around 5m where the dive began.  On the way up we also came across a school of horse mackerel, said to be extremely common in the area and particularly so at this time of year.

Despite the warm waters, Izu Ocean Park is best avoided at weekends and holidays when the crowds flock to the dive centre.  On weekdays there are likely to be fewer (and perhaps more experienced) divers, while of course there is much more to see when there are less people underwater.  At first glance, IOP is a very basic dive site and not the most exciting, but one that I definitely wouldn’t mind exploring again.

Practical information

  • Take the Shinkansen bullet train to Atami from either Tokyo or Shinagawa stations.  The early morning train from Shinagawa leaves at 7:34 (destination Nagoya) and arrives at Atami around 8:12.  A single ticket with non-reserved seat costs around 3500yen.
  • From Atami, take the Izu Kyuko line to Jyogasaki Kaigan station.  The journey is around 54mins and costs 880yen for a single ticket.
  • Our dive shop Little Ritz ( came to meet us at the station and drove us to the shop about 5mins away.  Here we could organize equipment, work out what we needed, pick up any rental gear, have coffee and get ready.  The shop is also a place for writing up log books, looking at photos and buying things like books on marine life.
  • Little Ritz then drove us to Izu Ocean Park (with a stop at the nearest convenience store to buy snacks and lunch) which is about 15mins away.  The park’s main dive shop is the IOP Diving Center ( which sells books, tiny items like pens or waterproof bags, and postcards which they will laminate so you can post them at 20m.  One postcard including lamination costs 100yen.  Outside the shop is a huge area of parasols and picnic tables.
  • We chose a couple of picnic tables and set out our bags and equipment.  Nearby are salt water swimming pools, a shop selling noodles, ice cream and soft drinks, a bath (do not enter wearing a wetsuit!), six or so showers, indoor shower area with lockers, and toilets.  You can also get changed into your wetsuit in this area.
  • The tanks can be found down the hill from the picnic tables.  Carrying all our equipment and wearing our wetsuits, we walked down to that area which is right next to the entry point.  Here, you pick up a tank and set everything up.
  • Entry is along a rope by foot.  Wearing all equipment including mask, fins and mouthpiece, walk facing the rocks and holding on to the rope.  The water is choppy, the ground is slippery, and when there is a queue of divers, entry can be extremely slow.
  • Ascend along another rope directly opposite the entry point.  Hold onto the rope and when it gets shallower, pull yourself up and walk back along the slippery ground.  Once it is safe to do so, remove mask, fins and mouthpiece, and finally equipment.  After swapping the tanks, all equipment can be left there while you take a break.
  • Little Ritz provides tea but no snacks or lunch so remember to prepare this beforehand!  Lunch is usually eaten between the first and second dives.
  • All divers are responsible for their own equipment.  Up the small hill from the entry point is an area to wash BCs, regs, fins, masks and snorkels.  Wetsuits, vests and hoods can be washed in a shower and hung close to the picnic tables.  All equipment is usually brought back and hung close by.
  • Two beach dives cost 12,500yen (rental equipment separate).  Any additional dive is 5,000yen per dive.  Renting full equipment costs 4,000yen, mask and snorkel 500yen each, fin and boots 500yen each, wetsuit 2000yen, reg 1000yen, BC 1000yen.

August’s dives

Dive 1: IOP: depth: 11.1m, dive time: 52mins, water temp: 23C, entry time: 11:07, exit time: 11:59, average depth: 4.7m, used a 10L steel tank, 2kg weights, 5mm wetsuit, 2-3mm hood/vest, BC wing.  Start pressure: 200 bar, end pressure: 80 bar.  Saw cardinal fish, sawtails, nudibranchs, anemones, camel shrimps and crabs.

Dive 2: IOP: depth: 20.2m, dive time: 45mins, water temp: 23C, entry time: 13:14, exit time: 14:00, average depth: 11.6m, used a 10L steel tank, 2kg weights, 5mm wetsuit, 2-3mm hood/vest, BC wing.  Start pressure 190 bar, end pressure: 40 bar.  Saw squid laying eggs, an orange sea slug laying eggs, horse mackerel and two types of nudibranch.

2 thoughts on “August 2012: Izu Ocean Park (IOP), Izu Kogen, Shizuoka, Japan

  1. Magnus

    Hey, I went there as well! Didn’t realize that it was a postbox when I looked at the map. We saw tons of morays and a napoleon wrasse. I liked that there was lots to see even in the shallow areas, it made the dive last longer. Have you converted to wing diving now btw? I’ll have to try that some day, maybe even this weekend. I’m going diving on the swedish west coast with a few friends. Have a good one Bonnie!


    1. Rising Bubbles Post author

      Hey! Sounds like you saw a lot more than we did that day 🙂 The postbox is a really cool idea, and there are some great finds around the rocks, especially the big ones. Curious to hear more about diving on the swedish west coast, let me know how that goes!



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