An 8-foot adult lemon shark moves through the shallow waters of Atol das Rocas' lagoon, a ray of hope for the expedition. It appeared for some time that there were no adult sharks to be found. With luck, those that are here will be sampled, tagged and tracked.

The longlining crews were back at work today, rotating in shifts to closely monitor the 30+ hooks dangling in Atol das Rocas's shallow lagoon. Scent streams flowed from the baited hooks, permeating the water with the smell of barracuda steaks. If there was a large lemon shark here, how could it resist?

Over the radio, one of the research team's excited voices began relaying information about a dramatic, bloody spectacle. They were witnessing an event so rare that even Samuel "Shark" Gruber, a 35-year shark veteran, had never seen it -- lemon sharks mating. Within an hour, I managed to make my way to the team's location.

As I approached their skiff, it was hard to tell that they had just witnessed such a dramatic incident, or that there was life onboard at all. The crew had been out since 9am, shelterless in the boiling sun. Most people wore their shirts like long, protective turbans and rested, sipping on water as often as they breathed. But, no one complained, not once, even when it was time to pull anchor and go check the hooks...again.

Sharks have to swim in order to live -- they stay moving to force water through their gills. Swimming is as important to them as breathing is to us. A hooked shark, unable to swim, will eventually drown. So, the longliners must vigilantly check the hooks every hour. No one wants a shark to die, especially on their watch.

The hooks did not come up empty this time around, but the shark on the line was not the species we were after. As luck would have it, the team had caught a nurse shark. So, I slipped into the water to have a closer look while the rest of the crew worked on freeing the animal.

Nurse sharks, although interesting in their own right, are not part of the expedition's research focus. In some respects they are actually a nuisance, taking away from time that could otherwise be spent looking for the elusive lemon shark. With so many nurse sharks in the area, the mission has been jokingly dubbed "the curse of the nurse."

After parting company with the longlining crew and the hooked nurse (who didn't seem to like me too much), I headed out with Gruber to see if we could finally track down some large lemon sharks.

Within minutes, we were successful, an 8-footer in the shallow water right next to our skiff! Again, I jumped in to meet it, expecting the shark to turn toward me. Instead, I found that it was more interested in leaving than chewing on my leg. I grabbed a few hasty photos before it disappeared.

As I climbed back onto the boat, Dr. Gruber yelled, "Now, no one can say those big sharks aren't here. They're here! We've seen them! What an exciting day, first the mating now this!"

We took off to see if we could find the shark again, moving at a good clip through the lagoon. Suddenly, our boat lurched and the outboard motor let out a loud, high-pitched scream. I turned in time to see the engine tumbling through the air upside-down. The spinning propellor swung dangerously close to Gruber, and then the engine plunged into the lagoon. Somehow, the renegade motor had worked its way free of our transom, and now it was under five feet of salty water. Today, it seemed, the expedition was being cursed by more than nurse sharks.

Gruber radioed for assistance from the other team, while researcher Guilherme Barbosa and I surfaced the drowned motor. With an engine first-aid kit onboard, we were able to dry out the spark plugs and drain the water from the pistons, but had no chance of getting the thing running again, not in our position.

Confronted with fleeting daylight and a stranded skiff, the mission's crew moved into action. They navigated the atoll's dangerous channel and unpredictable ocean swells to reach the interior lagoon, transferring crew and gear from skiff to skiff, then to a 13-foot Boston Whaler waiting off shore.

After towing the disabled skiff through the wildly meandering channel, we were on our way home, all hands safe, to the R/V SEWARD JOHNSON. Another day in paradise!