WELL, WERE BACK IN HAWAII, but this time to film the charming but benign subject of turtle-cleaning stations.
A nice change from the big dangerous sharks with big gnashers that we filmed last time we were here (Diary 1, January).
Turtles being the charming animals that they are, this is to be a pretty sequence of blissed-out turtles and light-dappled reefs - a nice feeling of harmony in nature. What could be more harmless A pleasure to film... or so we thought.
Green turtles are among the worlds great ocean wanderers, journeying across thousands of miles of tropical waters to return to their native nesting beaches. This makes them a perfect subject for Endless Blue, the open-ocean film of the BBCs forthcoming South Pacific series.
In this programme, we look at the challenges of survival in Earths largest ocean, where distances are vast, and food may be hard to come by.
We have local advice on where the cleaning station is, and hope that if we spend enough time there, and go nice and quietly, we will get to see (and film) some turtle action.
First day on site, and as cameraman Richard Wollocombe and I drop in things dont look too bad. Its early in the morning, so the light is still a little low, but the vis is pretty good.
We need to be early to be sure to catch the turtles coming in for their morning scrub. We
swim quietly toward the cleaning station and, amazingly, a turtle is right there, swimming
lazily by.
A few surgeonfish move towards him and try to follow, but he doesnt stop - hes obviously not in the mood for a clean.
Its a promising start, and a relief to see our subject so early on. We back off a bit from the area and hover close to the substrate, keeping a low profile while we wait for another turtle to show up The fish are going about their business on the reef, and its quite a pretty scene - but no turtles show up. After a while, we adjourn to hang out above a large rocky outcrop at 12m, conserving bottom time while we watch and wait... and wait.

DESPITE THE 28° WATER I start to get chilly due to the sheer inactivity of neutral buoyancy, and Rich is looking pretty bored. After 100 long minutes of hanging around, its time to go up.
Back on the boat, it starts to cloud over - not good for filming. Morning is turtle time, and it isnt going to clear up before noon, so we call it a day. Its a disappointing start, but we have topside filming to do in the afternoon, so our best bet is to get on with that.
We hope this wont become a trend...
Next day, the sun is shining and were ready for another morning of the turtle vigil. Dropping in, we make our way over to our favourite spot, approaching slowly to avoid scaring any turtles that might already be around.
Not a turtle is in sight, so we settle in by our familiar rocky outcrop and wait.
About 15 minutes into the dive, Rich catches sight of something off in the blue. Its about 20m to the wall, and we can just make out a large, pale shape moving off in the gloom.
Scoping the area, I satisfy myself that no turtles are about to pitch up and start getting cleaned the moment our backs are turned.
We can take a couple of minutes to fin over to the drop-off and see whats going on. Like moths to the lantern, were drawn to the edge of the wall.
After about a minute of peering into the blue gloom, we see a shape moving at the edge of our visibility. It looks large, but then things always do under water - its probably just a grey reef shark, but its always nice to see them, and a welcome change from seeing no turtles all morning.
I see the shape again. Its swimming nearer, and as it does so it becomes more defined.
Its a tiger shark, unmistakable in its markings, and ominous in its size.
Rich starts filming, but it disappears again into the blue. We stay peering out from the wall, trying to make out shapes.
Just as I think its gone, I see the shark again, this time swimming about 10m off the edge of the wall, and in our direction. It passes us by and continues about another 15m, but then it turns, heading directly towards us.
It really is quite large - more than 3.5m, and bulky. Rich is about 3m away from me, and closer to the drop-off, with his eye to the viewfinder, filming the shark. He doesnt immediately see that a second shark has appeared from nowhere, and
is also swimming straight in our direction.
I have a full view of everything and, with no camera to occupy any part of my brain, these two large predators have my undivided attention.
Suddenly weve gone from a quiet morning on the reef waiting for turtles to show up, to a
full-on shark dive with one of the top three iffy shark species.
With Rich filming the sharks as they bear in on us, theres not much to do but stand our ground. Swimming away might send out the wrong signals, making us look submissive.
Its impossible to determine their motives, but they are taking an active interest.
I consider what I have with me that might be useful in some way. Um, nothing. No shark-billy this time. Id like something to prod them away with that isnt actually my hand, but all Im holding is a flimsy piece of neoprene (the camera white-balance card), and the knife in my BC doesnt seem that much better. I look at Richs giant 1m-long, 35kg camera with envy.

AS THE FIRST SHARK BEARS IN on Richard, the other one approaches the two of us from the side.
Swimming steadily towards him, peering into the lens, shark one is only just over half a metre from Richards camera when he realises quite how close it is. He gives a small involuntary reaction, startling the shark, and it turns off to one side.
Im relieved, but I can hear a pulse thumping loudly inside my hood as the second shark heads steadily towards me. It seems so loud that the shark can probably hear it too.
But as it gets closer, it curves off to the side, cruising past about 3m to my right.
Both sharks circle back round over the edge of the drop-off and out of sight, but theyre soon back, approaching to about 3m away, and circling around us. They keep this up for a good few minutes, then disappear off over the reef and beyond the edge of our visibility.
The moment has passed, but my pulse is still pounding. I deliberate about what to do next. Are we in real danger, or were they just curious Perhaps they were attracted by the electronics of the camera.
There were no signs of aggression, but most sharks dont take a blind bit of interest in divers, and that wasnt the case here.
There was no bait in the water, so its clear that they were interested in us for our own sake, but in what capacity Rich and I look at each other, and move in a little from the edge of the drop-off.
Just then, one of the sharks reappears and heads towards us, but this time it doesnt come so close, half-circling us at a distance of about 6m before it swims off again.
Its a tricky situation - on the one hand, its a stunning shark and a rare opportunity for some great footage, but on the other hand its a big predator thats taking rather an active interest, and were not set up for a serious shark dive.
I know Rich has the cameramans urge to film, but for once Im not so disappointed when my computer tells me that I havent long to deco. The decision is made: its time to go up - you cant argue with the laws of physics!
As we head back to the boat, our new friend pays a few more visits. She half-circles us, but doesnt come in close. I suspect that this is an unhealthy interest. As we pass the cleaning station, theres not a turtle in sight, and I figure that weve found our reason.
Back on dry land, we get another surprise when we review the footage. The video cuts through the vis better than the naked eye, and we clearly see a third shark off in the distance in one of the shots.
Over the next few days, we go on to film the green turtle cleaning sequence we wanted. Its a delight to see the turtles revelling in their clean-up, as yellow tangs and black surgeonfish flock to remove the algae from their shells. We see another tiger shark only once, just passing, and not close.
Speaking to local divers, we realise that weve been treated to a rare close encounter. One tiger shark is sometimes seen in the area, but its usually off in the distance and doesnt approach.
One diver told us that hed never seen a tiger up close in more than 800 dives around the island.
Everyone is amazed that we have just pitched up and seen these sharks at such close quarters; they cant believe our luck.
Then, a few days later, we learn that there has been a sport-fishing tournament. Local boats have been chumming the area to draw in the big fish.
It seems to have worked.