What surprises owners who moved down from the Chesapeake or New England is that there is no winter shutdown here. Water temperature in Biscayne Bay bottoms out around 68-70°F in January and climbs past 86°F by August. Barnacle larvae never fully stop setting. A boat that got hauled twice a year up north needs a diver on a calendar cycle down here, year-round.
The May-through-October window is where boats get away from owners
Growth rate is not linear across the year. From roughly May through October, when surface temps sit in the mid-80s, barnacle set on a neglected hull goes from invisible to fingernail-catching in about three weeks. We have opened up 8-week intervals in July on boats that were spotless in February at the same interval and found acorn barnacles with hard bases already cemented into the paint.
The practical move is to tighten the cycle seasonally. Run 4 weeks from May to October, then back off to 6 or 8 weeks from November through April if your paint and usage support it. Owners who keep one fixed interval all year either overpay in winter or fall behind in summer. Neither is necessary.
A second summer factor: rain. Heavy wet-season runoff into the canals off the Miami River, Little River and the New River drops salinity and dumps nutrients. That combination feeds soft growth — slime, green hair algae, tunicates — fast. A boat at a Miami River dock can grow a full green beard in 10 days after a week of afternoon storms.
Your slip location matters more than your paint brand
Two identical boats with identical paint foul at very different speeds depending on where they sit. Open-water slips with real tidal exchange — Dinner Key, Crandon Park Marina, Haulover, the outer docks at Bahia Mar — flush themselves. Dead-end canal slips in Coral Gables, Keystone Point, or the back of Hollywood’s residential canals do not, and the water sitting against your bottom paint at slack tide is warm, still and biologically busy.
Dock lighting is the other one nobody warns you about. If your slip has bright dock lights burning all night directly over the water, you will grow more on the shaded side of the hull and around the waterline than the boat next to you in the dark. It is not a myth; we see the difference between adjacent slips constantly.
Running gear runs on a different clock than the hull
Props, shafts, struts and trim tabs are bare or nearly bare metal, and barnacles love them. Even on a well-painted hull, a set of props can go from clean to noticeably fouled in three to four weeks in summer. You feel it before you see it — vibration at cruise, a couple hundred RPM you cannot find, fuel burn creeping up.
Zincs are the other independent clock. In Miami-Dade and Broward marinas with heavy shore power and a lot of neighbors, shaft and trim tab anodes routinely need replacing at 3 to 6 months, not annually. This is why we check zincs on every visit and quote them on site rather than guessing from the dock — we have pulled shaft collars that were half gone at four months in one marina and near-full at eight months two miles away.
Schedule around your use, not just the calendar
If you have a Bimini run, a trip to Islamorada, or a tournament coming up, book the cleaning 3 to 7 days before you leave, not the day before. That gives you time to act on what the diver finds — a chewed-up zinc, a ding in a blade, a missing prop nut cotter pin. Cleaning the morning of departure means you learn about a problem with the boat loaded and the crew waiting.
Also schedule a cleaning after any long layup. A boat that sat three weeks while you were out of town has a bottom that does not match its calendar age. Same with boats coming back from a Bahamas trip and sitting straight into a canal slip.
What a recurring schedule actually costs you
Our rate is $4 per foot for boats 31 to 50 feet (with a $120 minimum for boats 18 to 30 feet) and $5 per foot from 60 feet up, paid after the work is finished, with before and after photos every visit. A 38-foot boat on a monthly summer cycle is $152 a visit. Stretching that to 10 weeks does not save money — it produces a hull that needs aggressive scrubbing, which pulls ablative paint off faster and shortens the life of a bottom job that costs thousands.
Zincs, props and running gear work are quoted on site, so you see the part and the condition before you approve anything. The photo set from each visit is also the easiest way to track whether your interval is right — if the “before” shots are clean slime and nothing more, you can stretch. If there are hard barnacles, tighten up.
Tell us your marina, boat length and paint type and we will suggest an interval that fits. WhatsApp us at (786) 756-0304 or call (305) 978-1440 — we have been diving these hulls since 2004, and the crew is bilingual.