Editor's note: Advertiser science writer Jan TenBruggencate has been accompanying the scientific expedition of the National Oceanic and Atmospheric Administration ship Hi'ialakai into the Northwest Hawaiian Islands. Here are his responses to questions from Advertiser readers:

Q. How different is the underwater scene than what we see on the main islands? Are there different types of coral, seaweed and fish? What about invasive species like roi and ta'ape — have they made their way over to those islands? And I always hear about how abundant the predatory fish like ulua and sharks are. Is it true?

— Lance Uchida

A. Two answers to the fish question. It seems that there are more fish and more different kinds of fish in a single location. At Nihoa, which lacks a barrier reef and is hit hard by storm surf, there's not much coral, and there are big, round boulders on the bottom.

French Frigate Shoals, by contrast, is Coral Central. And there are kinds of coral that are not found in the main Hawaiian Islands, like the table coral, acropora. Ta'ape goes right up the archipelago, all the way to Kure Atoll. Roi only gets as far as French Frigate Shoals, according to Randy Kosaki, chief scientist for this mission. And yep, lots of ulua and lots of sharks.

As I write this, I'm two hours from having swum with a Galapagos, several gray reefs and white-tip sharks.

Q. Our class came up with the question: Do the scientists on the Hi'ialakai have free time? And what do they do during their free time?

— Liane Ono and her second-grade class at 'Aikahi Elementary School

A. The scientists are a busy group, collecting samples and doing research during the day. And at night they record data, repair gear, process photographs and preserve their biological samples for study later when they get back to their own laboratories.

But some of them have time to kick back. I saw one playing an 'ukulele at sunset. Another group sat on the sides of an inflatable boat and chatted. The ship shows videos at night, which you can watch in your cabin or in the aft mess area, which is kind of a living room with a large-screen television and a coffee machine.

Q. I'm curious: How would this trip compare to your trip through the Northwest Islands on Hokule'a? More fresh food to eat (because of refrigeration)? Do you try to catch any fish while under way? How's your bunk? (I imagine your computer is staying a lot drier). How does the feel of the movement of the vessel differ, or feel the same? How's the weather been? Must be lots easier to stay on your hygiene. ... How are meals done? Do you have a kitchen crew? How's the body feel, and the mind? Different kind of exhaustion compared to working Hoku?

You guys take care now. No be teasing those ulua.

— Aloha and a hui hou, Leimomi Kekina

(Reporter TenBruggencate and Kekina stood the same watch when the voyaging canoe Hokule'a sailed through the Northwestern Hawaiian Islands two years ago.)

A. Hi, Momi,

The islands are the same, but the experience is very different. For a small vessel, Hokule'a is quite stable compared to NOAA's Hi'ialakai, which rolls quite a bit. I was never seasick on Hoku, but my first two days on Hi'ialakai were tough.

I have a bunk bed and a small cabin that I share with fish genetics expert Brian Bowen. It's quite a bit more comfortable and dry, compared to our hatchtop bunks with the leaky canvas on Hoku. And we share a small bathroom with the folks in the next cabin. There's a freshwater shower — quite a change from cold, saltwater bucket baths on the canoe.

Food is excellent, thanks to chief steward Allen E. Gary and his staff. They serve three hot meals a day, there's always hot coffee, fruit, juice and ice cream (yep, refrigeration is nice). Gary also is an expert fisherman and supplements chilled, frozen and canned goods with fresh fish. His hand lines are often trailing behind the ship during daylight when the vessel is well away from the islands, out of the no-fishing zones of the Fish and Wildlife refuges, state waters, and Coral Reef Ecosystem Reserve preservation areas. When the ship has to enter these areas, an announcement from the bridge over the public-address system warns him to bring in his fishing gear.

Hokule'a tucked right in to anchorages in the lee of islands, while Hi'ialakai stays well out to sea, so the islands, when you can pick them out, are specks on the horizon, and reefs are just distant white spots where waves break. You only see islands up close if you're in one of the small science launches. Being on the launches is more like being on Hokule'a: wet and exposed.

The weather is, as always, changing. It was so wild at Nihoa that we abandoned efforts there after a day. We had a fair day at French Frigate Shoals, but did an overnight run to Gardner Pinnacles in hopes of catching some good weather there, since there's no barrier reef to break the swells. It was so rough, with powerful currents, that we headed back to French Frigate. Only limited work could be done due to south winds and swells on the first day, but then it calmed down, and all three research boats are out with crews of scientists mapping coral disease patterns, collecting electronic buoys that record movements of tagged fish, taking clippings off designated forms of marine life for genetic studies, collecting crustaceans and so on.

A day of diving and working, followed by an evening of recording data, or in my case writing newspaper stories, is exhausting, but unlike aboard Hokule'a, we're not also standing watch and sailing the ship. The fatigue is there, but it's not as significant as on Hoku.

Q. First of all, thank you for all of your essays and updates. I have traveled all the Hawaiian Islands in my live-aboard sailboat. The memories of those ocean crossings were incredible. Wow, I wish I were there. There is one thing that stood out for me, and that was seeing the Southern Cross hanging almost ethereally in the lower sky. I traversed the night ocean; I remember actually being able to see the Milky Way. It has been said that on most Honolulu nights, only about 20 stars can even be seen. The last time I could remember seeing all the stars in our Northern Hemisphere, before the ocean, was hiking and backpacking in the great high plains of Utah for over 20 years. Blue-water sailing, oceangoing navigation and seeing the stars, I feel, will exist in only a few places anymore. But it sure is worth going that extra mile to see these glories of nature. I am so envious, but your updates bring great memories to mind.

— Helen Eschenbacher, Honolulu

A. Thanks for your informative note. Some of the crew and scientists have developed a habit, in the hour or two of light after dinner, of gathering on the ship's fantail and chatting as they look out over the sea, the clouds, the setting sun. There's been great stargazing in the evenings.

As for diving, I'm one of the very few uncertified tank divers aboard. But I've had a lot of fun snorkeling above the divers as they work, and slipping among the coral heads and shelves to catch glimpses of the amazing array of marine life.