Navigating the Florida Keys: Inside or Outside Route?
Date Posted: April 10, 2023

Extending in a sweeping southwesterly curve from Miami and the mainland, the Florida Keys offer a cruising experience unlike any other waterway area. In many ways the Keys resemble the islands of the Bahamas except for the main highway and 42 bridges. Cruisers have two options when navigating to the Keys:

  1. Inside Route: Stay on the ICW following Biscayne Bay and the sounds to their western ends then pass under the Card Sound Road Bridge and on into Florida Bay following the chain of the Keys along the bay side. 
  2. Outside Route: Enter the Atlantic Ocean from Biscayne Bay at either Cape Florida Channel or Angelfish Creek then follow the Hawk Channel westward around Key Largo and continue on along the ocean side of the Keys.

With either choice, cruisers can switch from one route to the other at Channel Five or Moser Channel, on each side of Marathon and west from Marathon. 

This choice is not a simple one. Each skipper must evaluate conditions and make the appropriate decision If taking the inside (ICW) route, slow down and keep a close watch on the depth sounder as depth changes of up to 1.5 feet are common in strong winds In Florida Bay and elsewhere in the Keys. Note that these changes are greater than tidal effects and must be taken into consideration in planning a passage along the ICW on the Inside Route. Obviously in depths of 4 to 5 feet MLW a reduction of 1.5 feet is significant.

Along the bay side stretch of the ICW from Tavernier Creek to Shell Key, you can expect some of the shallowest conditions you will see anywhere on the ICW system with charted depths of 4.5 to 5 feet MLW. To make matters worse the bottom conditions along this stretch are charted as "rocky." For boats that draw over 5 feet we recommend the Outside (Hawk Channel) Route (or "keep to the ocean side* as the locals might say).

Wind strength and direction are other critical considerations. Prevailing winds in the Keys generally have an easterly component. In the summer a southerly component is added, whereas a northerly component is more common in the winter. (Note this is based on probability and is not a prediction.) If winds have either an easterly or southerly component at more than 10 to 15 knots expect choppy conditions in the Hawk Channel (Outside Route). In northwest to north-northeast winds the Outside Route will be the more comfortable route as the westerly curve of the keys will provide more protection. 

On the Inside (ICW) Route, cruisers can expect better protection, at least in the closed sounds and basins initially followed by the ICW until things open up north of the Matecumbe Keys. Here the fetch increases and cruisers will experience chop in north to southwest winds. Chop is of particular concern on the inside route as effective water depths will be reduced by the boat's bobbing motion. In east through south-southwest winds the Inside Route is well protected by the unbroken chain of the Florida Keys. 

The final consideration, which is well known by seasoned Florida Keys mariners, is that the unbroken chain of the Florida Keys blocks the movement of water as well as waves. The water in the large expanse of the Florida Bay is landlocked on the north, east and south. Strong winds from any of these directions will push the waters of the shallow bay from one side to another creating "wind tide" conditions.

Some cruisers may opt to visit both "sides" of the Keys via a roundtrip. Be aware that depth and clearance restrictions will make some harbors and marinas inaccessible, particularly to sailboats. Careful planning of anchorages and provisioning stops can influence your routing decisions.


We've outlined both the Inside & Outside routes for navigating the Florida Keys in depth in Chapter 3 of our Florida Keys Waterway Guide covering everything from cruising conditions, navigating channels, to bridge schedules and Goin' Ashores. Purchase a printed copy of the Florida Keys guide or purchase a Print + Digital subscription, for everything you need for your cruising adventure to the Florida Keys.

Comment Submitted by TONY SMITH - April 15, 2023

I have a 30 ft pilothouse cruiser and I always travel inside. Florida Bay and Biscayne Bay are huge bodies of water. Shallow is the word-----3 ft depth is not uncommon. Pay attention to your depth sounder and stay in the channel. It is a beautiful trip either way and rarely gets more than a moderate chop. Generally it's a flat sea with no big rollers. Anchoring is usually good.....hard sand. We use a sharp claw Delta with some big chain and we never drag.

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