From the 14th January to the 7th February 1943, Japanese forces conducted Operation Ke for the evacuation of their troops from Guadalcanal. At this time the I-1 was on station in the area of Cape Esperance, where she was detected by the New Zealand ships RNZN Kiwi and Moa.
The Kiwi and Moa dropped depth charges and drove the I-1 to the surface. A close quarter battle ensued to the point of small arms being used. The Kiwi eventually rammed the I-1 damaging her conning tower and pressure hull. She was then forced onto a nearby reef. The crew set destruction charges but they failed to completely destroy the I-1. In the following weeks the code books were retrieved from the wreckage and US intelligence was able to complete the code that was partly broken during the Battle of Midway.
Of further significance was the back-up or reserve codes which were also retrieved. The combination of these enabled US intelligence to intercept Admiral Yamamoto and have his aircraft shot down killing the Admiral.
A lot of history for one wreck. The I-1 was salvaged during the 1960s and 70s and with a lot of non-ferrous metal onboard a lot of destruction took place. It is still a good dive and the stern of the wreck easily defines what she was.
The I-1 lies in 3-28 metres and is dived from shore - this requires a 200m swim from shore to the site. The drive from Honiara takes about 45 minutes normally, but will take an hour at least when bridges have been damaged or washed away.