Be mesmerised by bay's icy grandeur
The massive cracking noise is dead ahead. Not the thunderous sound expected, but it commands attention nonetheless.
A chorus of involuntary gasps and "oh looks" follow, with much finger pointing, before the rest of the small crowd scurries to the portside rail.
Cameras and smartphones go into video and photo overdrive.
The constant creep of ice and debris down the mountainside has finally resulted in what we are all waiting for: a calving - the breaking off of a piece of glacier.
On this brilliant summer's day in Alaska, we are witnessing this phenomenon at the face of Margerie Glacier - one of the US state's best-known and most photographed landmarks.
Because tidewater glaciers can move more than 1.5m a day, calving can happen a few times an hour here.
So high up on the open bow deck of Holland America Line's MS Volendam, the calving seems almost in slow-motion. We mistakenly think the falling mass is of little significance compared with the overall size of the glacial "river".
Our sense of scale is all out of whack in the massive natural theatre that is Glacier Bay National Park.
The displaced "chunk" is now an iceberg that's probably the size of a small truck. A flock of seagulls is taken by surprise and hurriedly has to change course to avoid being crushed under the weight or being hit by icy shrapnel as some of it explodes on impact on rocks below.
Only 250 years ago, Glacier Bay did not exist. A river of ice more than 160km long covered the entire area. By 1750, the Little Ice Age had helped the glacial advance reach its maximum, jutting out into Icy Strait and well past what is now Bartlett Cove Visitor Center, 105km from the state capital, Juneau.
Captain George Vancouver, who gazed upon the 8km inlet in 1794, described the phenomenon as "a sheet of ice as far as the eye could distinguish". As the glacier retreated north, the area it had carved out filled with saltwater, forming the fjord that is more than 300m deep.
Today, it's another 88.5km from the visitor centre to view the seven tidewater glaciers. But the world here is still wild, remote and untamed.
The hours we spend in this special part of the world are included in our seven-night Inside Passage Alaska cruise.
Our bucket-list adventure truly begins in the morning as we traverse Icy Strait, where the glacier extended as late as 1780, and travel through Sitakaday Narrows, past numerous islands, coves, bays and inlets, as well as mountains more than 1000m high.
Commentary by Glacier Bay park rangers and the Huna cultural interpreter is broadcast to outside decks, the Crow's Nest bar (with a bird's eye view) and stateroom television, and combines with a main stage presentation so no one misses the details of the grandeur around them.
The early mist and dramatic clouds - hanging low like fluffy cotton wool over pyramid-shaped mountains - make us feel like we are wilderness pioneers experiencing this wonder for the first time.
The basalt mountains seem to be circling us. Embracing us. Allowing us to uncover their secrets, little by little. They are far from lifeless, with an emerald blanket of vegetation falling almost from the top of jagged peaks to teal-green waters below.
The enormity and the majesty of the setting cannot be overstated. We are miniscule in Mother Nature's grand palace.
We tick off the landmarks: Gloomy Knob (406m) at 7.50am, Lamplugh Glacier near the 2066m Mt Cooper at 8.55am, John Hopkins Inlet at 9.10am.
Traditional Dutch pea soup is brought around by Volendam staff to warm our insides on deck.
Thermal underwear, jeans, thick socks, boots, scarves, gloves and woollen coats over hooded jackets still let in some of the cold air. But we are steadfast at our post, with eyes peeled for wildlife - or at least their telltale signs, including the spray from a humpback whale's spout.
Brown, grizzly and black bears, moose and mountain goats roam the park, otters, seals and humpback whales rule the waters, but all we see today is birdlife including a lone bald eagle and curious seagulls - some hitching a ride on a floating platform of ice.
Our ship glides past Russell Island into Tarr Inlet for a closer look at the Grand Pacific Glacier.
The glacier's creep down the mountain has brought so much debris from subsequent rockslides and avalanches that brown, grey and charcoal swirls and tracks in the ice look like a four-wheel-drive convention has passed through.
It is so surreal, so alien to our knowledge of Earth. We feel like space travellers discovering a new planet.
Even at mid-morning, the undisturbed setting throws off delicate reflections, blurred slightly by the soft ripples of the flowing water.
We change course, and an incalculable number of small icebergs appear, like shredded coconut or icing sugar sprinkled across a blue cake. These natural ice "sculptures" are mesmerising.
A trio of puffin birds greet us as we take up position at Margerie Glacier at 10.45am. As the ship slowly manoeuvres closer, Margerie reveals her snaking path from sky to bay.
The ol' girl is about 1.6km wide with an ice face of 76m above the waterline and a base that is 31m below sea level.
The thick, turquoise-tinged rows of icy columns at the face stand shoulder to shoulder like sentinels creating an impenetrable fortress. Time stands still as we pay our respects at this vision of Margerie and gaze up to the top of her mountain, where she was born in an ice age.
We feel privileged to have been introduced to her - and her stately home - at least once in our lifetime. It's been a cracking good day.