Lock 23

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Dive Site Report: Exploring Lock 23 – A Tale of Two Locks

In the heart of the St. Lawrence River lies a unique dive site that promises both historical intrigue and underwater adventure. Although it goes by the title “Lock 23,” this site is home to not one but two locks that have witnessed the passage of time, revealing the rich history of the region. Join us as we delve into the depths of this fascinating underwater world.

The site known as “Lock 23” boasts not one but two locks: the first, the smaller Rapide Plat Lock, was constructed in 1847, while the larger Lock 23 was completed in 1905. These locks stand side by side, creating two distinct areas for divers to explore. But that’s not all; there’s also a hidden inner channel that leads to the foundations of the municipal hydroelectric plant. As you descend into the depths, you’ll encounter a myriad of posts, cribbings, piers, boathouses, and shoreline structures, each with its own story to tell. Keep your eyes peeled for intriguing artifacts and relics scattered throughout the underwater landscape.

One of the most remarkable aspects of this dive site is the presence of historical remnants left behind by time. The gates of both locks were dismantled in 1959 to make way for the Seaway flooding, and the buildings and machinery that once adorned their walls were removed. Much of this debris found its final resting place within the lock spaces, where it remains to this day. As you explore the underwater terrain, you’ll have the opportunity to witness these preserved fragments of history.

Lock 23 offers a unique diving experience throughout the seasons. Water temperatures become comfortable for wet-suit divers by mid-June, hovering around 60°F/15°C. As summer progresses, the water warms to at least 72°F/23°C by mid-August, providing ideal conditions for your underwater excursions.

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Currents play a significant role in the site’s dynamics. While the St. Lawrence River always has a current due to its natural flow, the strength of the drift can vary. The control dam at Iroquois, located 12 km upstream, influences the current speed. Divers can expect a consistently strong current at the tops of the locks, created by water flowing around and over the walls. However, inside the old lock and hydroelectric plant channel, back eddies provide some respite from the current, and by the time you reach the boathouses and wharves, there’s hardly any current at all.

Visibility at Lock 23 is generally good, with an average range of 10-15 feet. While conditions can occasionally vary, the site remains easy to view and explore. The deepest part of the dive site reaches just over 40 feet, while the tops of the walls are less than 15 feet deep. It’s worth noting that the St. Lawrence shipping channel lies beyond the lock walls and is significantly deeper.

Along the shoreline, you’ll encounter underwater flora, with small weeds in the spring growing into a submerged forest by the end of summer. These weeds, however, pose no entanglement risk, as they can be easily removed with a gentle tug. While they may be a minor inconvenience during entry and exit, they add to the unique charm of the Lock 23 dive experience.

Intriguing and historically rich, Lock 23 offers divers an opportunity to immerse themselves in the past while exploring the underwater mysteries of the St. Lawrence River. Whether you’re a seasoned diver or new to the sport, this dive site promises an unforgettable journey beneath the surface.