Underwater Hull Cleaning at Sèmè Terminal
Full hull cleaned in the water, vessel stays on hire
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Tell us the vessel, the port and the window. Scoped reply, usually the same working day.
Cleanship Marine provides underwater hull cleaning at Sèmè Terminal, Ouémé, working the tanker waiting area off the terminal and sea area outside the SPM safety zone. Commercial dive teams remove slime, weed and shell growth from the vertical sides, flat bottom, bilge keels, sea chests and niche areas with the vessel afloat and on hire — no dry dock, no diversion, no off-hire.
Sèmè Terminal is the export end of the Niger–Benin crude pipeline, operated by WAPCO, a CNPC subsidiary. Crude from Niger's Agadem fields arrives by pipeline and is loaded onto tankers at an offshore single point mooring; the first cargo loaded in May 2024. It is a single-purpose oil terminal rather than a port, served from Cotonou a short way along the coast.
A crude tanker comes to Sèmè in ballast to load, and that is the useful fact for hull work. Sitting light, she has less hull underwater than she will for the whole laden voyage that follows, so the wetted area to clean is smaller and the job shorter — and she then takes a clean bottom into the leg where drag costs the most fuel. The clean is done in the waiting area before she is called to the buoy, never inside the terminal's safety zone and never while she is connected. With no harbour craft at Sèmè itself, the dive support boat runs out from Cotonou.
What it gets you
- Hydrodynamic smoothness restored before fouling reaches the calcareous stage that damages coating
- Fuel and emissions penalty from drag reduced without taking the vessel off hire
- Documented condition record for the technical file and the next docking specification
- Sea chests and inlets cleared, protecting cooling water flow
Working conditions at Sèmè
Sèmè has no harbour at all. Tankers load offshore at a single point mooring, so every vessel here lies in open Gulf of Guinea water with nothing between her and the long-period Atlantic swell that runs onto this coast. That swell, not visibility, decides whether a dive goes ahead. The water itself is warm and — away from the lagoon outflows further west at Cotonou — clearer than the harbour ports, which helps inspection work on the days the sea allows it. No work is ever done at the buoy or while a tanker is connected.
- Where we work
- Tanker waiting area off the terminal · Sea area outside the SPM safety zone
- Vessels we see here
- Crude oil tankers · Mooring and terminal support vessels · Offshore supply and crew boats
What we do at Sèmè
- Pre-clean fouling survey to establish coverage, growth type and coating condition before any tool touches the hull
- Brush cart cleaning of the flat bottom and vertical sides, with brush hardness selected against your antifouling specification
- Hand cleaning of bilge keels, rudder, stern frame, thruster tunnels, anodes and the niches a cart cannot follow
- Sea chest gratings and inlet openings cleared of growth and debris to restore cooling water flow
- Diving permission cleared with WAPCO, the terminal operator and the terminal before mobilisation
- Before-and-after video and stills, with a written report on coating condition and anode wastage
Planning the window at Sèmè
The combination of Atlantic swell and rain governs the calendar at Sèmè Terminal, with the heaviest rain from May to October and swell running year-round. The swell here is long-period Atlantic ground swell rather than wind-driven sea, so it reaches the anchorages on days that look calm from the bridge and it is the single biggest cause of a lost in-water window on this coast. The buoy itself is off limits, so hull work is done with the tanker in the waiting area off the terminal, before she is called to the SPM or after she is released; the dive plan is built around the loading schedule and the swell.
Work is taken at the tanker waiting area off the terminal and sea area outside the SPM safety zone, and which of those a vessel ends up at changes the dive plan more than the season does. Teams mobilise via Cotonou (COO), so give us the ETA as early as you have it — the travel is the flexible part, the approvals and the working window are not.
What we typically find at Sèmè
Liquid and gas tonnage here spends long stretches at the terminal or waiting for a slot, so growth tends to be even and well established across the hull rather than patchy — heavier than the trading pattern suggests, and further along than a speed report alone would indicate.
Tankers coming to Sèmè have usually crossed from their last discharge in ballast and may then wait offshore for their loading slot, and it is that waiting in warm Gulf of Guinea water that adds growth fastest. A clean done before loading removes it before the laden voyage, where it would cost the most.
Standard scope of work
Included as standard on every underwater hull cleaning attendance, wherever the vessel is. Anything outside it is quoted separately and flagged before mobilisation, never added afterwards.
- Fouling survey
- A pre-clean dive establishes fouling type, coverage and severity, and confirms coating condition so the correct tooling is selected.
- Flat bottom and vertical sides
- Brush cart cleaning of large areas, removing slime, weed and shell growth to restore surface smoothness.
- Niche areas
- Hand cleaning of bilge keels, bow thruster tunnels, rudder, stern frame, anodes and other niche areas where fouling concentrates.
- Sea chests and gratings
- Sea chest gratings and inlet openings cleared of growth and debris to restore cooling water flow.
- Documentation
- Underwater video and stills before and after, with a written report covering coating condition and anode wastage.
How we deliver it at Sèmè
- 1
Scope and vessel details
Tell us the vessel, her particulars, the coating specification and the window at Sèmè. We come back with a defined scope, a crew size and a duration we will stand behind. Where the conditions here will not support what has been asked for, we say so at this stage rather than after mobilisation.
- 2
Permits and approvals
Access at Sèmè Terminal is the terminal operator's decision as much as WAPCO, the terminal operator's, so both are in the approval chain from the start — a berth-side refusal discovered at the gangway costs the whole attendance. Diving permission, terminal approval and any environmental clearance for in-water work are handled by us, not left with the agent to chase.
- 3
Mobilisation to Sèmè
Divers, compressors, brush carts and cameras mobilise via Cotonou (COO). Where a vessel is also calling at Cotonou, one mobilisation is normally sized to cover both.
- 4
Safety setup and the dive
The vessel is secured for diving — main engine, shaft and thrusters immobilised, sea suctions confirmed shut, permit agreed with the master. Teams work under surface supervision with continuous diver communications and video throughout.
- 5
Report and handover
A completion report covering underwater hull cleaning is issued with before-and-after imagery, coating and anode condition and anything found that you should know about. The findings are discussed with the vessel rather than emailed and forgotten.
Sèmè Terminal at a glance
- UN/LOCODE
- BJSEM
- Port type
- Private Port
- State
- Ouémé
- Country
- Benin
- Water body
- Bight of Benin, Gulf of Guinea
- Port authority
- WAPCO, the terminal operator
- Main cargoes
- Crude oil
- Crew mobilisation
- Cotonou (COO)
- Services here
- Hull Cleaning
Frequently asked — Underwater Hull Cleaning at Sèmè
Do you provide underwater hull cleaning at Sèmè Terminal?
Yes. Cleanship Marine works Sèmè Terminal (BJSEM) in Ouémé, Benin, covering the tanker waiting area off the terminal and sea area outside the SPM safety zone. Teams mobilise via Cotonou (COO) with the full spread.
Can the hull be cleaned while the tanker is on the Sèmè buoy?
No. Nothing is done at the single point mooring or while the vessel is connected and loading. The clean is done in the waiting area off the terminal before she is called in, or after she has been released, and it is agreed with WAPCO and the master beforehand.
Can underwater hull cleaning be done while the vessel works cargo at Sèmè?
No — nothing is done while a tanker is connected to the buoy and loading. Hull work is done in the waiting area off the terminal before she is called in, or after she is released, which at Sèmè is usually time she is spending waiting anyway. The vessel stays on hire throughout, and there is no diversion and no dry dock. We scope against the conditions at Sèmè and tell you honestly whether the window you have is enough.
Do you need a diving permit from WAPCO, the terminal operator?
Yes, and we obtain it. Diving permission from WAPCO, the terminal operator, terminal approval where the berth requires it, and any environmental clearance for in-water work are arranged as part of the job rather than left with the agent. The master's permit to work and the immobilisation of machinery are agreed on board before anyone enters the water.
What is underwater visibility like at Sèmè?
Visibility at Sèmè Terminal is good for this coast — open sea water, away from the lagoon outflows at Cotonou — so the limit here is the swell rather than what a diver can see, and the combination of Atlantic swell and rain sets the outer limits of the calendar. How the tide and sea state shape the dive plan is set out in full in the working-conditions section on this page.
Which vessels do you carry out underwater hull cleaning on at Sèmè?
Crude oil tankers, Mooring and terminal support vessels, Offshore supply and crew boats — the traffic at Sèmè Terminal runs to crude oil, so those are the profiles we see most. The scope is sized to the vessel, not to a standard package.
How quickly can a team mobilise to Sèmè?
Divers and equipment mobilise via Cotonou (COO). Give us the ETA and the window and we will confirm what is achievable rather than promise a date we cannot hold. Where the vessel also calls at Cotonou or Lomé, one mobilisation is often sized to cover both.
What does underwater hull cleaning at Sèmè cost?
It depends on the vessel's dimensions and wetted area, the fouling state found, the coating specification and the working window available at Sèmè. We would rather scope it properly and give you a specific figure than quote a headline rate that changes once the work starts. Send the details and the window at Sèmè and you get a scoped price, usually the same working day.
Underwater Hull Cleaning at Sèmè Terminal.
Tell us the vessel, her ETA at Sèmè and the window. You get a scope, a crew size and an honest duration — usually the same working day.