At boat shows, you will typically see (especially on larger yachts) a "Tall Rig" and an "ICW Rig". The difference in these two rigs is the height of the mast.
With the current push towards taller and taller spars in search of the performance benefits of high aspect ratio rigs in upwind sailing, mast heights have towered higher than ever before! This might be great for a performance enthusiast, but what about someone who wants to retire on a floating condominium and cruise up and down the ICW? All of a sudden, a 70 foot mast becomes even more of a burden and the new yacht owner is banished to offshore cruising when they would really rather just marina hop up and down the coast.
Yacht builders have this one figured out, offering "ICW Rigs" that have a shorter mast, usually in the range of 63 feet in height. This is because the advertised bridge height is 65 feet, so having a few feet of clearance will let you transit the bridges with ease!
The false advertising is that these bridges are only 65 feet at low tide! In the Carolinas, the tides will be close to if not greater than 5 feet, meaning that the bridge may suddenly become 60 feet of clearance. Being a fixed bridge, there is no bridge tender to call on the radio, instead you must wait for the tide to go out before you can transit the bridge.
We have a mast height of less than 60 feet, so we feel comfortable (although it is always unnerving) passing under the bridges at any tide, thanks to the bridge clearance signs at the starboard bridge abutment. As the tide rises or falls, the numbers become visible so that way you know how high the bridge is at that moment.
If you are looking to cruise the ICW in retirement, I would caution away from a giant floating palace with a very tall "ICW Rig" and instead opt for something with a mast below 60 feet in height. This will make your life so much simpler as you can pass under the fixed bridges as you arrive at them instead of trying to make the next bridge before the tide comes up again.