Tales from the Logbook--The Sharks of Nigali Passage

 

In October 2017, I joined my friends Brandon and Melissa Cole and others for a nine day trip around the Fiji archipelago on the live-aboard dive boat, Naia. I made 27 dives during the trip.  Some of the most memorable were on Monday, October 16 and Tuesday, October 17 at Gau Island.  My dive journal for the first day cryptically states, “Nigali Passage, Shark Day.”  We stayed in the area a couple of days and made three dives to specifically observe sharks.  The experience, which could have been dubbed “Sharks on Parade,” did not disappoint.

Dive Log

Date	Dive Number (Trip)	Depth	Duration
October 16, 2017	14	91	45
October 16, 2017	15	85	47
October 17, 2017	18	87	45

Dive Planning

We gather around the Muster Station early in the morning for a briefing on our dives in the Nigali Passage.  The passage, which cuts through the island’s barrier reef, connects Gau island’s lagoon to deeper water.  The sharks and other marine life use that corridor to move between the two areas.

The best time to dive Nigali Passage is 1.5 hours either side of low tide when current and visibility conditions are optimal.

A schematic of the Passage drawn on a white board used for site briefings shows the general plan for the dive.  The tenders will take us outside the Passage, drop us into deeper water (about 80-90 feet) near the bottom of the passage.  We will then move up the passage toward the lagoon with the wall on the right.  We will cross a sand channel and end up at a ledge in about 60 feet of water called “The Bleachers.”  The flat terrace creates a platform or bench from which we can observe the grey reef sharks (Carcharhinus amblyrhynchos) as they move through the Passage between the lagoon to deeper waterand white tip reef sharks (Triaenodon obesus) as they rest on the bottom pointed into the current.  From the Bleachers we will ascend toward the lagoon, turning right at the top of the channel. 

The grey reef shark typically reaches about five to six feet in length.  It feeds on small boney fish, cephalopods, and crustaceans.  They are often seen in groups swimming slowly ‘upstream’ in current swept reef channels by day. When threatened, grey reefs sharks lower their pectoral fins, arch their backs and swim in an exaggerated manner.  They are considered quite easy to approach by divers with non-threatening movements. 

The Dives

We don our wetsuits on board the NAIA.  We finish gearing up in the rigid inflatable boat (RIB) that serves as a dive tender taking us from the mothership to the dive site.  With everyone on board, the tender motors into the Passage.  I am buddied with Michelle.  We back roll off the rigid hull inflatable boat and descend to 80+ feet.  Near the bottom, a big school of barracuda swim by in what seems like an endless procession.  We start swimming up the passage toward the lagoon assisted by the current caused by the water moving into the lagoon on the flooding tide. 

We pick out our spots in The Bleachers and settle in.  Tucked into the Passage wall, we have an unobstructed view.  Michelle would later remark “it’s like being in a wildlife blind.”  I agree.  We are not really detectable to the sharks except for our exhaust bubbles. The sharks seem to materialize, moving down the Passage, some very close by.  They seem to move with a magnificent deliberate slowness that befits a skilled predator.  You can almost hear the “oohs” and “aahs” of the divers as the big fish move past us.  One grey reef shark cruises over our position but takes no notice.  

I know that these reef sharks are generally not a threat to divers.  Still, for a moment I experience an atavistic response to its presence—a bit of apprehension mixed with a rapt fascination.  I have encountered similar sharks on many of my dives and my reaction is always the same.

After about 20 minutes, which passes much too quickly, it is time to begin my ascent. Michelle and I move up the very steep channel assisted by the current.  At the top of the channel we turn right.  Visibility is somewhat by sand grains suspended in the water.  As it clears we see the “cabbage patch” a seemingly endless expanse of cabbage coral.  We surface, climb back on board the tender, and head back toward the NAIA.