On 17/18 February 1944, the nine fast carriers of U.S. Task Force 58 made a surprise 2-day air raid on the Japanese forward fortress of Truk Lagoon – far out into the Pacific. Operation Hailstone began with 72 USN Hellcat fighters launching in darkness for a dawn initial fighter sweep of the lagoon. After one of the largest dogfights of WWII, the Hellcats had cleared the skies of Japanese fighters – allowing successive waves of dive- and torpedo-bombers to sweep over the lagoon and attack the now vulnerable shipping below. More than 40 Japanese transport ships and destroyers were sunk – filled with their wartime cargoes of tanks, trucks, shells, munitions. Made famous by Cousteau in 1969, Truk Lagoon is without doubt the greatest wreck diving location in the world.

You can read more about Truk Lagoon and its amazing wrecks in these 2 books

Here are some videos of diving some of these famous wrecks:

Hanagawa Maru

The 4,793-ton transport ship Hanagawa Maru was anchored at the fuelling dock on Tol Island, Truk, offloading her volatile cargo of aviation gasoline in 55-gallon drums when she was attacked by four TBF torpedo bombers from the carrier Bunker Hill during Operation HAILSTONE by the 9-carriers of Task Force 58. One torpedo hit her on the starboard side of Hold No 2. The explosion ignited her dangerous cargo and blew a large hole in the side of the ship. She sank quickly, ablaze. Today the wreck of Hanagawa Maru sits upright in 30 metres of water.

IJN Oite
The 1,400-ton Imperial Japanese Navy destroyer Oite was attacked by U.S. Grumman Avenger torpedo bombers as she entered Truk Lagoon on 18 February 1944 having rescued more than 500 crew from the light cruiser IJN Agano. She was hit amidships by an aerial torpedo as she made an evasive turn to starboard at full speed. She broke her back, split in two and sank quickly with great loss of life. Her wreck lies on 60+metres of water up towards North Pass.
Shinkoku Maru – engine room
An exploration of the vast multi-deck level engine room of this WWII Japanese naval oiler sunk by U.S. Task Force 58 aircraft on 17 February 1944. Entering through the fatal bomb hole low in her port side aft that sank her, follow as the divers move along corridors and staircases as they ascend to the higher levels.
IJN I-169
The large Imperial Japanese Navy submarine I-169 was present in Truk Lagoon on 4 April 1944 loading stores when an alarm was issued of a U.S. air raid. The submarine went to crash dive – but all the deck hatches had not been closed. Her control room flooded and she sank to the bottom of the lagoon where she lies today in 35 metres of water.
Shotan Maru
1,999grt Type 1D standard cargo ship
IJN Fumizuki
Mutsuki-class destroyer – the 1sr class to be fitted withType 93 Long Lance 24-in torpedoes
Amagisan Maru
7,600grt passenger-cargo vessel. Bombed and torpedoed on 17 February 1944, setting her cargo of 55-gallon drums of fuel on fire.
Gosei Maru
1,931grt standard coastal freighter attacked at anchor off Uman Island on 17 February 1944. She took an aerial torpedo hit from a USS Monterey torpedo bomber, listed and rolled over onto her port beam ends as she sank.
Unkai Maru No 6
3,220grt naval auxiliary transport attacked at anchor on 17 February 1944 in the 6th Fleet anchorage north of Uman Island. She was set ablaze but remained afloat. She was attacked again and sunk the following day.
Momokawa Maru
Medium sized naval auxiliary transport sunk on 18 February 1944 by U.S. Curtiss Helldiver dive bombers from USS Bunker Hill
Unidentified IJN salvage & repair tug
This 300-tonne tug was only found in late 2018 and now sits upright in 30 metres. She remains unidentified at this time.
IJN Oite
-a tour of the stern section of this destroyer
San Francisco Maru
This large 5,831grt passenger cargo vessel is one of the oldest wrecks in the lagoon – and perhaps the most famous. She lies in 65 metres of water still filled with her cargo of war supplies, tanks, howitzers, artillery, beach mines, bombs and muntions
Aikoku Maru
This large 10,500grt 492-feet long passenger cargo liner was dive bombed on the morning of 17 February 1944. She had more than 800 Japanese troops in make ship billets in her aft holds and superstructure. Her forward holds were filled with munitions – and that is where she took a dive bomber hit that set off a catastrophic secondary munitions explosion that vapourised the forward section of the ship. There was only 1 survivor from crew and troops. She sits in 65 metres today.
Rio de Janeiro Maru
This 9,600grt passenger cargo liner was bombed and sunk on 17 February 1944 and now rests on her starboard beam ends in 35 metres.
Nippo Maru
This 3,764grt Japanese freighter casualty of U.S. Operation Hailstone sits in 45-50 metres with a Type 95 HA GO light battle tank deck cargo in front of the bridge.
Heian Maru
This large 11,616grt cargo liner was being used as a submarine tender when she was attacked and sunk by U.S. dive and torpedo bombers on 18 February 1944.
IJN Oite – stern section
The Kamikaze-class destroyer Oite had rescued more than 500 crew from the torpedoed light cruiser Agano and was entering Truk Lagoon through North Pass when she was attacked by Task Force 50 aircraft on 17 February 1944. An aerial torpedo split he ran two and she sunk into 60 metres of water.

Seiko Maru
The large 392.5-feet long IJN auxiliary transport vessel Seiko Maru was launched on 14 May 1940 as Japan readied itself for war in the Pacific. She had her machinery, engine and boiler rooms at the stern – so she resembled a tanker or oiler.
On 17 February 1944, as Task Force 58 fast carriers launched their surprise 2-day raid codenamed Operation HAILSTONE, she was at anchor in the IJN Fourth Fleet anchorage north east of the man-made aircraft carrier shaped Eten Island. A valuable target she was quickly attacked and took bomb hits aft from USS Enterprise Douglas Dauntless dive-bombers that blew out both sides of her hull. 
She was set ablaze and settled by the stern into 52 metres of water, where she now sits upright and largely intact – barring the bomb damage aft.