The growing buzz of aircraft engines disturbed the Japanese military construction personnel hauling equipment ashore on the beige coral sand of Tulagi Island at 8:20 AM on May 4, 1942. Offshore, the large IJN (Imperial Japanese Navy) minelayer Okinoshima, flagship of Admiral Shima Kiyohide, lay at anchor, along with two destroyers, Kikuzuki and Yutsuki, and transport ships. Six Japanese Mitsubishi F1M2 floatplanes also rested on the gentle, deep blue swell, marking Tulagi's future as an IJN floatplane base. The men on the beach, at inland construction sites, or aboard the Japanese ships, looked up towards the huge white cumulus clouds sailing on the ocean wind. Taken completely by surprise, the Japanese stood and stared as 13 sturdy-looking dive bombers dropped through the cumulus layer at 6,000 feet, plunging towards the IJN ships. As they streaked lower, the white star on a black disc insignia of American aircraft grew visible on the underside of each wing. As the dive bombers roared low, drowning out the soft clacking of palm-fronds agitated by the steady sea breeze, the dark capsule shapes of 1,000-lb bombs broke away from their undersides and hurtled towards the anchored ships. Amid the sudden thunder of explosions, huge fountains of white foam gushed upward, sparkling in the tropical sunlight before collapsing back into the sea. Only as the American Douglas SBD-3 Dauntless dive bombers began climbing out of their attack did the Japanese finally open fire with the four anti-aircraft guns set up on the Tulagi shore.