Blynman Canal

The entire passage, generally referred to as the Annisquam, is frequently an attractive alternative to the trip out around Thatcher's Island.


The Blynman Canal, connecting Gloucester Harbor to the head of the Annisquam River, has existed in some form since the 1640s. Twentieth century improvements to the canal and dredging in the river make for a useful shortcut through the base of Cape Ann from Gloucester to Ipswich Bay.

The entire passage, generally referred to as the Annisquam, is frequently an attractive alternative to the trip out around Thacher Island. With a strong wind or heavy sea from the north east, the waters off Cape Ann show the effect of their full exposure to the Atlantic, making the shelter of the Canal a welcome respite or a good time for lunch. In a flat calm, the intricate scenery along the banks provides a welcome diversion for the crew while under power.

For the sailor on a schedule, one hour of motoring through the Annisquam can save three or four hours outside. The summer breeze has a knack for following the shoreline of Cape Ann, such that we often find ourselves beating east through Sandy Bay, south past Thatcher’s, and still beating west past Gloucester and Manchester, wishing we had taken the Canal.

📷 Geoff Rand
📷 Geoff Rand



On a summer weekend, hundreds of boats pass through the Canal without difficulty. And while the trip is uncomplicated in most conditions, the volume of traffic should not lead to a sense of complacency. Shoaling in the dredged portions of the river meant a controlling depth of maybe 4 feet on an average low tide {2007}. The shallowest spot is between the cans north of Flashing Green “25”. The channel leading north out of the river and into Ipswich Bay is also dredged, and was good for about 8 feet on an average low {2010}.

The skipper of a deep-draft sailboat not intimately familiar with the Annisquam will avoid passage within an hour or two of low tide. Scheduling your first trip for a rising tide offers a significant measure of comfort. We know of at least one 40 footer that found the edge of the channel on a falling tide, leaving the two men aboard unexpectedly huddled together under the spinnaker through a chilly October night.

Currents in the Annisquam are strong in places, but the typical inboard auxilary will handle them readily, except as discussed under Bridges, below. The current floods in from both ends simultaneously, meeting in the marshes just north of the Railroad Bridge. If you’re counting on an small outboard to push your sailboat through, timing the passage to go with the currents will give your motor a lot less to whine about.

From the Blynman Bridge right through to Annisquam Light, very little weather finds its way in. The water is flat, and the wind is muted as the river twists by the land close on either side. Such calm can be deceptive as you prepare to head out to Ipswich Bay. Motoring past Annisquam Light in a strong northerly puts you into a narrow channel with a fairly unforgiving lee shore on either side.

Not for navigation

Anchorages & Moorings

Both are available outside the canal, in Gloucester Harbor. There are moorings in Annisquam.


Cape Ann Marina is an extensive facility with deep-water slips between the Blynman and RR bridges. Somewhat incongruous among the marshes, it is sheltered, convenient for the sailor bound either direction the next day, and just over a mile walk to town.

📷 Geoff Rand
View of the Annisquam looking south from the 128 bridge. Notice how closely the shoals encroach on the narrow channel.

Route 128 Bridge

Three bridges cross the Annisquam/Blynman. Furthest north is the highway bridge carrying Route 128, with a fixed vertical clearance of 65 feet. Given the unusual combination of a spar tall enough to hit the bridge and a keel shoal enough to clear the bottom, it is a rare boat that needs to worry about the 128 bridge. Those who do should measure their rig carefully and be sure of the tide.

Railroad Bridge (VHF 13)

Known on the radio as “Gloucester Railroad Bridge”, the bridge necessarily caters to trains first and boats second. When you hail, the bridgetender will give you an idea of how long before he can open. During weekday rush hours, commuter rail traffic on the Rockport line may keep the bridge closed 20 minutes, forcing boats to point into the current and wait.

The opening is dauntingly narrow and the channel makes a 90 degree turn at the span, but it’s not hard to negotiate. The real worry is oncoming traffic. Boats coming with the current are said to have right of way, but the direction of the current is not obvious around slack water, nor is the rule universally observed.

Sometimes the bridge tender will direct traffic. Listen closely to channel 13 to get a sense of traffic on the other side. Oncoming boats will frequently help too, by telling you when it’s clear behind them. Put someone on the bow for a better view.

Blynman Bridge (VHF 13)

The Blynman Bridge crosses the canal at Gloucester Harbor. Southbound boats, headed out of the Canal, have right of way, and boats in the harbor wait, fairly reliably, until the outbound traffic has cleared.

The easiest time to go through is at slack water surrounding high tide. A strong favorable current is no great benefit, making it trickier to wait for the bridge, and requiring speed on top of the current to maintain control.

A strong head current can take all of an inboard’s efforts just to get through the bridge. Inevitably, the 3 motorboats ahead of you will gun their engines successively harder, accelerating the current under the bridge into a seething wash that can spin a boat sideways. Wait a few moments for the maelstrom to subside before following them through.


📷 Geoff Rand
For sailboats, the narrow opening of the railroad bridge is further constricted by the need to keep the mast clear of the single lifting span.
📷 Geoff Rand
Gloucester harbor opens up just beyond the Blynman Bridge.


Not for navigation. Charts are not updated. 


Fitting Out

Cape Ann Marina, on the west side between the Railroad Bridge and Blynman Bridge, has transient slips, plus a full range of supplies and services available. New for 2007, their fuel dock carries diesel as well as gas. If you’re headed through the Annisquam anyway, this is the quickest access to fuel in the area.


Cape Ann Marina
VHF: 10




If you have updated information, corrections, or contributions to this harbor, please share them below. Comments are moderated by Boston Sailing Center. 

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Rand Peck
1 year ago

I navigate the Annisquam often and you’ve created an excellent guide, paricularly concerning the RR Bridge and Blynman Bridge. However, you’ve misspelled “Thatcher”. This is a family name and is spelled Thacher as in Thacher Island.
Reply to  Rand Peck
1 year ago

Thanks for letting us know. It’s been corrected.

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