I had been diving Truk every year continuously since 2007 up to Feb 2015, sometimes multiple trips of two weeks or more per year, and one year (2013) back-to-back after an expedition to Bikini Atoll. The diving is that good, but with the unfortunate caveat being the wrecks now undergoing stages of imminent final collapse after well over 70 years. The popular wreck's (Shinkoku Maru, Fujikawa Maru, San Francisco Maru etc) bridge superstructures' are disintegrating; some of the big wrecks sunk lying on their sides (Heian Maru, Rio de Janeiro Maru), their hulls especially at the bow are sagging & about to shear away. Be attentive during the pre-dive briefings, stay with your dive guide and again be in control with good neutral buoyancy & non-silting frog kicks if you penetrate inside.
Be especially aware on wrecks with high octane Aviation Gasoline Drums --The Hanakawa Maru for instance has deteriorating/leaking AvGas drums in the cargo holds; you can see the whitish gasoline layer suspended in the water column with bright ambient light, but sometimes you can inadvertently swim thru the layer while traversing a dark corridor. The most concentrated, nastiest and hazardous places are the upper corners of enclosed bulkheads where undiluted AvGas percolates up into & collects (
I've suffered a caustic chemical 2nd degree wrist burn by accidentally sticking my hand up through this stuff on the Hoki Maru).
And lastly, don't be tempted to go inside the Fumizuki Destroyer engine room, or the I-169 Submarine aft hatchway on Backmount single tank -both over 30m/100' deep and very tight, silty & treacherously restrictive passageways- unless you are Sidemount doubles trained with advanced wreck certification. (The two popular tech advanced wreck deep dives -
Aikoku Maru and
Oite Destroyer- at 60m/200', as well as the wreck sites at the Fourth Fleet anchorages starting at 45m/150' are usually not visited by the Liveaboards, unless during a rare tech week charter. You can try to arrange a dive on them "a la carte" through Truk Stop Hotel/Truk Lagoon Dive Center or Blue Lagoon Dive Shop land based operations, either with pick-up from the Truk Odyssey Liveboard for example, or optionally staying land based at the respective dive-ops' hotels).
If all you had timewise was one week, then the
Truk Odyssey would be the best way to visit all the popular wrecks within non-technical recreational depths (5 to 6 day itinerary, at least 3 dives on a particular wreck site/or 3 different wrecks per day). You will have the option to do the
San Francisco Maru aboard the Truk Odyssey Liveaboard, but again unless you have technical diving certifications, they probably won't let you use their 11L AL80 twinsets and Eanx50/Oxygen deco gases. So in other words, you will be doing the San Fran Maru at 45 meters/150 feet deep --usually last dive of the week long itinerary-- on a single 11L AL80 cylinder (they do have larger 15L steel120 cylinders for rental as well) . . .and it will be an unsatisfyingly short bottom time of maybe 8 to 10 minutes with a few minutes of mandatory decompression on backgas starting around 12m/40 feet. Recommend bringing your own Oxygen Analyzer to check your Nitrox, or else you'll be waiting to use the dive-op's O2 Analyzer along with everybody else. Wear gloves, a full length skin suit 1 to 3mm thick with optional separate hood --all for jagged metal scrape/cut protection.