The slime film comes first, and it is not harmless
Owners who come down from the Chesapeake or Long Island expect to see barnacles before they worry. Down here the first layer is a brown or rust-colored biofilm — diatoms and bacteria — that feels like wet felt when you run a hand along the boot stripe. It shows up fast on the transom and the flats under the chine. That film is what everything else attaches to: barnacle larvae and tubeworm larvae look for a settled surface, and a slimed hull gives them one. It also drags. Owners with a 32-foot center console will tell us they lost two or three knots off cruise and assumed it was the engines before anyone looked underwater.
Barnacles find your running gear before they find your paint
Bottom paint, while it still has life in it, buys the hull some time. Your props, shafts, struts, trim tabs, bow thruster tunnel and the leading edge of the rudder are bare metal with nothing discouraging anything, and that is where we find the first hard growth on nearly every boat in Miami-Dade and Broward. A prop with acorn barnacles on the blade faces is unbalanced and inefficient, and on outboards the barnacles get up inside the anti-ventilation plate area and around the lower unit where you cannot see them from the dock. We clean the hull by hand with a brush and a hand scraper, and the running gear and other metal parts with a pressure machine, because the two surfaces foul differently and need different handling.
Tubeworms, bryozoans, and why the growth is different at the river
Barnacles get the blame, but calcareous tubeworms — hard white squiggles cemented to the gelcoat — are just as common and harder to notice until they have textured the whole bottom. Add lacy bryozoan crusts, hydroids that look like fuzz until you touch them, and soft tunicates on the underside of swim platforms and dinghy bottoms.
Location changes the mix. Boats in clean ocean-influenced water near Haulover or Bahia Mar see heavier barnacle and tubeworm settlement. Boats up the Miami River, in the Dania Cut-off Canal, or in the New River basins sit in lower-salinity water that favors algae, soft growth and, in some spots, small oysters along the waterline. A boat in a shaded covered slip in Keystone Point grows less algae and more hard growth; a boat on an open face dock in full sun at Crandon or Hollywood grows a green beard along the waterline fast.
The boats that foul fastest are the ones that never leave the slip
A boat used every weekend knocks some of its own slime off and keeps water moving over the running gear. The ones that sit from May to October — the owner is up north, the boat is in a slip in Aventura or Lighthouse Point — are the ones we show up to with a quarter-inch of growth on the struts and a bow thruster that will not turn. That is also when fouling stops being cosmetic: strainers and thru-hulls grow closed, raw water flow drops, and the first sign is an overheat alarm on the way out of the inlet. Speed paddlewheels and transducers foul early for the same reason.
How often, and what it costs to stay ahead of it
Most boats in South Florida do best on a monthly cycle; some lightly used boats in cooler months stretch to six weeks. Letting it go to three or four months means we are removing hard growth instead of soft growth, which is harder on the paint than regular maintenance ever is. Pricing is straightforward: $120 for boats 18–30 feet, which is our minimum service, $4 per foot for 31–50 feet, and $5 per foot for 60 feet and up. You pay after the work is done and you get before and after photos, so you can see what was actually on the bottom. Zincs, props and running gear are quoted on site once a diver has looked at them — anode wastage in warm, moving water here is its own variable.
We have been diving these hulls since 2004, we work at your dock or slip anywhere in Miami-Dade and Broward, and the crew is bilingual. If your boat lives on a mooring, bring it into a transient slip and we will meet you there. Send a WhatsApp to (786) 756-0304 with your boat length and marina, or call (305) 978-1440.