Sailing for more than two months across 3,000 miles of open ocean, the 102 passengers of the Mayflower—including three pregnant women and more than a dozen children—were squeezed below decks in crowded, cold and damp conditions, suffering crippling bouts of seasickness, and surviving on meager rations of hardtack biscuits, dried meat and beer.

“The boat would have been rolling like a pig,” says Conrad Humphreys, a professional sailor and skipper for a recreated sea journey of Captain William Bligh. “The smell and stench of illness and sickness down below, and the freezing cold on deck in the elements, it would have been pretty miserable.”

The Mayflower, like other 17th-century merchant ships, was a cargo vessel designed to haul lumber, fish and casks of French wine—not passengers. The 41 Pilgrims and 61 “strangers” (non-Separatists brought along as skilled craftsmen and indentured servants) who boarded the Mayflower in 1620 made for unusual cargo, and their destination was no less foreign. The ship’s square rigging and high, castle-like compartments were suited for short hops along the European coastline, but the Mayflower’s bulky design was a handicap for sailing against the strong Westerly winds of the North Atlantic.

“The journey would have been painfully slow with many days of being blown backward rather than forward,” says Humphreys.

Incredibly, though, all but one of the Mayflower’s passengers survived the grueling, 66-day ordeal, and the Pilgrims even welcomed the arrival of a newborn baby halfway through the journey, a boy aptly named Oceanus. The Pilgrims’ joy and relief on catching sight of Cape Cod on the morning of November 9, 1620 was recorded by their leader William Bradford in Of Plymouth Plantation.

“Being thus arrived in a good harbor and brought safe to land, they fell upon their knees and blessed the God of heaven, who had brought them over the vast and furious ocean, and delivered them from all the perils and miseries thereof," wrote Bradford.

The Pilgrim’s arduous journey to the New World technically began on July 22, 1620, when a large group of colonists boarded a ship called the Speedwell in the Dutch port city of Delfshaven. From there, they sailed to Southampton, UK, where they met the rest of the passengers as well as a second ship, the Mayflower. The two ships disembarked from Southampton on August 6 with hopes of speedy crossing to northern Virginia.

But just hours into the journey, the Speedwell began to leak badly, and the two ships were forced to pull in at Dartmouth. The Speedwell was finally ready to sail again on August 24, but this time only made it 300 miles before springing another leak. The frustrated and exhausted Pilgrims docked at Plymouth and made the difficult decision to ditch the Speedwell. Some of the Pilgrims also called it quits in Plymouth, but the rest of the passengers and cargo from the Speedwell were transferred to the already overcrowded Mayflower.

The traditional account of the Mayflower journey begins on September 6, 1620, the day it sailed from Plymouth, but it’s worth noting that by that point the Pilgrims had already been living aboard ships for nearly a month and a half.

The Mayflower was about 100 feet long from stem to stern and just 24 feet wide. In addition to its 102 passengers, the Mayflower carried a crew of 37 men—sailors, cooks, carpenters, surgeons and officers. The crew was housed in small cabins above the main deck, while the Pilgrims were consigned to the “gun deck” or “between decks,” a suffocating, windowless space between the main deck and the cargo hold below.

“These lower decks were very cramped, cold and wet, with low ceilings no more than five feet tall,” says Humphreys. “And all around you, people are getting seasick. It’s really not a very nice place to be.”

The passengers shared the gun deck with a 30-foot sailboat called a “shallop” that was stored below decks until their arrival in the New World. Between the masts, storage rooms and the shallop, the total available living space for 102 people measured only 58 feet by 24 feet. The passengers practically slept on top of each other, with families erecting small wooden dividers and hanging curtains for a semblance of privacy.

“The crew would occasionally let some of the passengers up on deck to get some fresh air, but on the whole, the Pilgrims were treated like cargo,” says Humphreys. “The crew were worried about people being swept overboard. The journey was difficult enough for seasoned sailors, nevermind novices like the Pilgrims.”

Mealtime on the Mayflower brought little to celebrate. The cooks would have run out of fresh food just days into the journey and instead relied on salted pork, dried fish and other preserved meats. Since regular bread would spoil too quickly, they served hardtack biscuits, jaw-breaking bricks made from flour, water and salt.

“The beverage of choice for many of these old voyages was beer,” says Humphreys, explaining that casks of fresh water tended to go “off” during long storage. “Even young children were given beer to drink.”

Subsisting on small rations of salted meats and beer, the Pilgrims would have been malnourished, dehydrated, weak and susceptible to scurvy. When Humphreys recreated Bligh’s 60-day crossing of the South Pacific, he and his crew ate only 18th-century rations—about 400 calories per person per day—and each man lost 25 percent of their body weight.

Bradford’s short description in Of Plymouth Plantation of life aboard the Mayflower is the only surviving account of the crossing, but it includes enough harrowing details to understand how close the journey came to disaster.

After a month of relatively calm seas and smooth sailing, the Mayflower encountered the first of an unrelenting series of North Atlantic storms that buffeted and battered the ship for weeks. The crew was forced on several occasions to lower the sails and let the Mayflower bob helplessly in the towering waves.

“They were encountered many times with cross winds and met with many fierce storms with which the ship was shroudly shaken, and her upper works made very leaky,” wrote Bradford, “and one of the beams in the midships was bowed and cracked, which put them in some fear that the ship could not be able to perform the voyage.”

Whether Bradford was talking about a cracked mast or another type of wooden beam is unclear, but the damage was serious enough for the Pilgrims to call a meeting with the captain to discuss turning back. But then something remarkable happened.

“…There was a great iron screw the passengers brought out of Holland, which would raise the beam into his place,” wrote Bradford, describing an object that was either the screw of a printing press or a large jack to raise the roof of a house. Either way, it worked, and the Pilgrims “committed themselves to the will of God and resolved to proceed.”

During one of those brutal storms, when the Mayflower was forced to draw its sails and “hull for divers days,” one of the passengers apparently became desperate for a breath of fresh air. Bradford wrote that a “lusty young man” named John Howland wandered onto the main deck and “with a seele [or pitch] of the ship [was] thrown into the sea.”

By some miracle, Howland was able to grab hold of the halyards hanging overboard and hold on for dear life, “though he was sundry fathoms under water,” wrote Bradford. Working quickly, the crew pulled Howland close enough to the ship to snag him with a hook and haul the foolhardy young man back onto the deck. Bradford proudly reported that after a short sickness, Howland not only recovered, but “lived many years after, and became a profitable member both in church and commonwealth.”

Bradford makes only passing mention of the one death on the Mayflower. A young boy named William Butten, an indentured servant to one of the Pilgrims, fell ill during the journey and died just a few days shy of reaching the New World.

Given the dangers of the journey and the rough conditions aboard the Mayflower, it was a miracle that only one person out of 102 perished on the 66-day voyage. Sadly, the Pilgrims’ fortunes changed for the worse once they landed at Cape Cod in early November. The passengers and crew continued to live on the Mayflower for months as permanent dwellings were constructed on the shore.

With each passing week, more and more Pilgrims and their “stranger” companions succumbed to bitter cold and disease. By spring 1621, roughly half of the Mayflower’s original passengers had died in their new home. Among them was little Oceanus. In one piece of good news, another baby named Peregrine, the first Pilgrim baby born in the Plymouth Colony, not only survived the brutal winter, but lived on for more than 80 years.