Black Water Dive®
Black Water Dive® is a kind of night diving. We are setting up underwater lights of high-color rendering on the sea bottom of night that while considering tides, times, places. The creature which appears is mainly juveniles and larvae. All is fascinating, and it's not to be seen at daytime or regular night diving. It will be your first experience.
"BWD" uses a lot of underwater lights, but its purpose is not to illuminate the underwater brightly without limit. The brightness of each light is limited to a maximum of 1500 lumen, which is about the same brightness as a commonly used underwater light. Then why use lots of underwater lights? It's for create a space of suitable light. Creature's phototaxis has nothing to do with light intensity. That is, even if it is not a strong light, Creature will gather sufficiently. Of course, if you are going to put together squid of pelagic, light needs to be strong. Creatures have finished floating stage period and are coming to the area to approaching to shore. We only need the minimum brightness to make it easy to find it. In fact, they are coming there even without that light.
The important elements are thoroughly the tide, time, and place.
*"BWD" stands for Black Water Dive®.
*Black Water Dive® is a registered trademark of Ryo Minemizu.
It was around 1990 that I was interested in these unknown creatures. Christopher Newbert's photo book "Within a Rainbowed Sea", which I purchased for the first time as an underwater photograph photo book, it was introduced a lot of beautiful coral reef landscapes and creatures, but the most interested thing among them the golden shining octopus and Blenniidae with red pectoral fin. All, most of the body is skeleton creatures. Since all were black backgrounds, I understood what was filmed in the sea at night. I was doing diving guide at the Izu peninsula in Japan at the time, so when I dive in the ocean of the night, I tried to see skeleton creatures like that in the photo book. In those days, when speaking of underwater lights it was a time when there were only Toshiba halogen lights that to put four D batterys.
A lot of elongated larvae of the mantis shrimp was crowded before the lights when I was trying several times only a Toshiba-light put upward from the bottom of ocean. In those days it was still film camera era and I was not able to take larvae of the unpredictable moving the mantis shrimp as a decent photographs, but I was very excited about the creature I saw for the first time. I tried secretly on several times, and I could also find Tholichthys stage of the Butterflyfish and juveniles of the Pearlfishe (at the time, I was thinking the larva is Congridae's). Yes, even Toshiba-light, which isn't bright, there was enough fish-gathering effect. The an era has changed, gradually a new type of underwater light come out. The groundbreaking was Apollo Sports made a lead battery type underwater light (still halogen). It was much brighter than Toshiba-light, and the battery was large capacity, so I could keep a long lighting time. And underwater lights using the HID bulb appeared, I purchased the CANNON 100 light made by Underwater Kinetics and tried it. This was a light of 12.5 watt HID bulb / 450 lumens, it was a well bright epoch-making at that time, and from now on I thought that the age of HID will come even to the world of underwater lights. With HID light, the amount of plankton gathered increased, but the ignition lighting was unstable and it was a weak point of HID. After that some new HID lights were released, but none of them was satisfactory.
Soon the age of LED underwater lights came. It's much smaller than HID light, and stable lighting, but the brightness is no way inferior. Immediately I bought FIX LED 1000 DX which FISHEYE released, after that changed to FIX LED 1500 DX later, I bought the FIX AQUAVOLT 7000 too. Because I was thinking to take effect that brighter is better. The AQUAVOLT 7000 boasted the largest brightness of 7000 lumen at that time, and stable lighting for more than 2 hours was possible at 4900 lumen when reduced the brightness to 70%. Of course there were big effects. I saw the first time Abralia andamanica and school of Todarodes pacificus, various Crustacea larvae, I continued new encounters keep every dive. But after that I come across RGBlue lights I am using now.
Phototaxis and favorite color
One day, I got the opportunity to try RGBlue LED light. RGBlue is an underwater LED light made by specialty to high color rendering to faithfully reproduce the original color of the object. Initially I was thinking of using it as a light for video shooting. But before that, I decided to compare three lights evenly put on the sea bottom. Lit each light of FIX AQUAVOLT 7000 (6,500 - 8,000 K) and RGBlue System 02 (5000 K / Ra 80) and RGBlue System 02 Premium Color (4200 K / Ra 95) on in the sea of night. FIX AQUAVOLT 7000 lighted at 70% 4900 lumen. RGBlue System 02 lighted at 1000 lumen of the second brightest from the bottom. RGBlue System 02 Premium Color lighted at 900 lumen of the second brightest from the bottom. Two types of RGBlue are much darker than AQUAVOLT 7000. However, the difference appeared relatively quickly. What! Clearly the RGBlue light that should be darker than AQUAVOLT 7000 had more creatures gathered. And the creatures that came to AQUAVOLT 7000 was immediately to attract toward the RGBlue light. As a result, we reveal that the belief that "the brighter the light is, the more creatures gather" was wrong. It was same result any time when changed the day and try it many times. Even among RGBlue, there was a subtle difference in the tendency of creatures to gather, which obvious related to was configured color. As a result the creatures like gathering to more natural light than artificial light. Even in that sense, RGBlue is an excellent light for creatures.
In Black Water Dive ®, I'm trying to keep mind the brightness of the light to 1500 lumen or less at the maximum and to use the high color rendering lights. Apart from that, we have established rules in our own that not to doing in the same place in daily. Specifically, for example, when doing four days of consecutive Black Water Dive ®, it is necessary to prepare four dive points. This is essential to avoid doing it consecutive in the same place. Also, if you do it in the same place as before, you can go only after at least one week. Also, if you went to the same place for two consecutive weeks like this, you can do it in the same place in the next eight weeks later. In other words, if the last was May, the next is July after eight weeks. In addition, we are deciding that it will be a total of seven days with do in the same place all year round. This is a consideration for avoiding "fixation of predator fish" that can occur by placing the light in the same place. All of these are own rules set based on experiences and examples of the past 20 years.