Slack tides occur when sea current neither ebbs nor flows. Every 6+ hours a high or a low becomes slack. This tide time neither pushes nor pulls. Its stationary movement yet not stagnant, it's stillness moves one to steadiness. Wind and waves still carry its surface in a direction, but its body and depth holds itself. Only still for a short period, a slack tide is a period pause between sentences. It punctuates flow like how music uses silence between its notes. Slack is the stillness between knots - a break in the action...the power of pause.
While this "non-current" holds a tied vessel in place by placing no pressure on decks, dock lines, anchor chains or rodes, the "stayed" / "standing" water loosens boats' ties as they stay tied. That concept is kind of weird to stay with. In short, when slack tide relaxes line tension, it may seem as if tide is sleeping. But water never rests for it is only transitioning between force and its flow direction. Life is often similar to current because it creates push / pull; tension / ease; tightening / loosening; highs / lows; liftings / lowerings; comings / goings and ins / outs. I think slack is Nature's way of catching its breath; the natural inhales and exhales of sea water.
Ironically, slack also occurs when a vessel no longer is floating - when it runs aground. Of course, any "grounded" boat can only move when high tide raises it off its bottom. So no grounded yacht can float anywhere until then. Then Nature takes its own sweet time to raise its water level. However, when a vessel grounds at highest tide, Nature needs mankind's assistance to pull it off.
Humans may want to get off a "hard" bottom to float their boat sooner than later, but they often need to be patient and wait the 6-hour cycle. Nature does not stress over human time. So in essence, whether they like it or not, humans become Nature's patient. Of course, many a skipper is unwilling to wait for Nature. Then when capatins refuse to wait for a lift-off, they ignore Nature and or their running into a shallow, they may suffer unintended consequences such as damaging a keel, prop or rudder. At a high tide grounding, a crew is usually more than ready to float their boat. Whether they are prepared is a completely different story.
As I slowly motored Mystique into Bimini harbor in early evening, the tide felt slack. Steering between the confusing entrance buoys was easy, but reading the duplicate lights seemed confusing. At least I felt fortunate Mystique was neither fighting against nor pulling us forward by tidal current. Neither an adverse nor a favorable water direction force would assist my steering Mystique into the dark of a foreign port. I did not want our vessel to labor against the tide or increase speed moving into a channel with limited mark lighting. So in a way, slack tide greeted us like an expectant host; it helped to ease our arrival. Or so it seemed at the time.
After 12 hours sailing 55 miles across Florida Strait’s 3-4 foot waves intoto the Bahamas on a southeasterly breeze, we had had a long day. Then in a sudden moment Mystique had crossed another challenge - a solid shallow shoal inside North Bimini’s Alice Town harbor.
Anyone can perceive a "grounded" boat as insecure, while anyone can see "grounded" on land as seeming secure. Any grounding in a narrow harbor in the dark with a swift current can be unsettling. But we were lucky tide-wise - it was not quite low slack. So we knew some time in a little over six hours, my boat would float off. In about twelve hours time, we calculated we would have a good chance of floating off.
As dusk and darkness descended upon Mystique, we entered Bimini harbor at around 7:30, only to be befuddled by blinking channel buoys conflicting with our GPS chart. As we approached the narrow entrance, I suddenly realized buoy locations, GPS and chart indicators were all different. All seemed to contradict the other. Hurricane Irma? So to say we entered North Bimini with some trepidation would be an understatement. To say we crept like a cautious crab along a shallow shoal would be not be an understatement.
It is rare that locations do not coincide somewhere on instruments and Explorer Charts, but when they do, they can make sweat glands work overtime. Almost none of the buoys appeared to collaborate what my screen and charts were telling me. All seemed out of place, then when we suddenly touched bottom for a moment, I wasn’t sure what to trust. Since seeing in pitch black darkness is always deceptive, relying on GPS can be better than charts. But when they conflict, it’s not time to guess!
The first clue was the GPS and reality did not coincide. Our charts were simply not gybing with what our eyes witnessed. The charts and GPS cited shifting sands, but noted nothing about new or shifting buoys or markers. Maybe Irma’s or Matthew’s Hurricane power had relocated them. Maybe my resources were both outdated. Maybe my memory was betraying me. Maybe doesn’t matter. Maybe is not good enough. The reason makes no difference to reality.
My instincts were to stay outside Bimini’s harbor, but when Mystique touched bottom and moved forward, we were again headed back into the narrow straightaway to starboard where our boat could safely anchor with a southerly. But good intention, wise seamanship or skilled navigation don’t position your vessel into a safe anchorage especially in the pitch of early night.
Actually our crossing from Florida to Bimini was mild in comparison. Caught on a low spot at low slack tide wasn't too bad, but it just wasn't the ideal anchoring situation we envisioned. Though our sudden surprise stop felt frustrating, we were still safe. I knew in a matter of a few hours the tide would begin to float us off. Yet to end a whole day sailing with a grounding wasn't the best way to begin our sailing adventure. While I knew basically we were close to our intended anchorage, it was still surprising the next morning almost 12 hours after our surreptious arrival, Mystique was stuck at "slack" near a couple of docks.
My anxiety level risen as my last memory of the harbor was in the early morning dark three years earlier when Mystique departed for West Palm Beach. A lot can change in that period of time. So when we ran aground in the what we believed to be the center of the harbor with the reverberating sounds of the Super Bowl, we anchored just in case. We knew at high slack tide Mystique might unstick before we woke. By 11:30 am we floated off the shallow.
So when I woke at 3:00 am, Mystique’s 30 degree tilt to port immediately suggested Mystique was even more “high and dry” than I thought. But our heel was helpful because it also gave me a clue about Bimini's tide table.
It wasn’t until 11:30 the next morning that Mystique moved out of the mud.
So what did I learn from this adventure:
- Don’t enter a Bahamian harbor at night, especially if there is any doubt.
- Don’t assume a chart and GPS are accurate or updated.
- Blinking red and green lights are not always entrances to a harbor.
- Don’t assume a harbor is the same it was three years earlier, especially at night.