The Pacific war began on 7 December 1941 with Japan’s surprise raid on the U.S. Pacific Fleet at Pearl Harbor. Simultaneously, Japan moved to seize large swathes of the Pacific including Malaysia, Singapore, Hong Kong, Guam and Wake. In early 1942 Japan embarked on a 2nd offensive to extend her empire and secure her position such that the Allies could never countenance the cost of retaking this vast area. But this 2nd offensive fatally overextended her capabilities – and Japan suffered crushing defeats at the Battle of Midway and the Battle of the Coral Sea in early 1942.
In August 1942, the Allies were ready to turn from defending against the Japanese expansion to their first offensive campaign, focused on an airfield under construction by Japan on Guadalcanal in the Solomon Islands from where Japan long range bombers could threaten Allied shipping moving between America, Australia and New Zealand.
The Guadalcanal campaign was long and bitter – lasting from 7 August 1942 until 9 February 1943. It involved three major land battles, seven major naval battles, the latter culminating in the 4-day long decisive Naval Battle of Guadalcanal from 12 to 15 November 1942.
So many ships were sunk in the channel off Guadalcanal that it became know as Iron Bottom Sound. You can read more about this campaign and its sunken legacy in Deeper into the Darkness
Here are some videos from diving its famous wrecks: