Decide
Which bottom usually gives the best holding for a recreational boat's anchor?
The lesson in plain words
- Shelter first
- Pick a spot with land between you and the forecast wind and swell, not just the wind blowing now.
- On Portugal's west coast the summer nortada blows from the north or north-west, and the Atlantic swell usually comes from the north-west, so bays open to the south give the best shelter.
- Ask what happens if the wind shifts during your stay.
- Bottom
- The chart shows the nature of the bottom.
- Sand and mud usually hold well.
- Rock, stones and weed hold badly and can foul the anchor.
- Avoid seagrass meadows: anchors and chain tear them up, and some are protected.
- Depth with the tide
- Check the depth at low water: you must stay afloat when the boat swings.
- Check it at high water too: the length of chain you let out depends on the greatest depth.
- The anchoring calculator works the length out from the high-water depth and the height of the bow roller.
- Room and rules
- You swing in a circle around the anchor, so keep clear of other boats, rocks and the shore.
- Do not anchor in a fairway, over charted cables or pipelines, inside the 300 m reserved for bathers at a bathing beach, or in marked or protected areas.
- DL 93/2018 art. 30 requires you to anchor in line with the official charts, the Capitania editais and the notices to mariners.
Key data
- Shelter
- From the forecast wind and swell, not today's
- Good holding
- Sand and mud
- Poor holding
- Rock, stones, weed; avoid seagrass
- Depth checks
- Low water to stay afloat; high water for scope
- Rules
- Charts, Capitania editais, notices (DL 93/2018 art. 30)
Key points
- Shelter from the forecast wind and swell, including a likely wind shift.
- Sand or mud; avoid rock, weed and seagrass.
- Enough water at low tide; scope from the high-tide depth.
- No anchoring in fairways, over cables, in bathing zones or where an edital forbids it.
Check what you have read
The forecast is a north-westerly force 5 this afternoon. Which bay is the better anchorage?
True or false?
Decide each statement before you see the answer.
Anchoring is allowed anywhere that is not a harbour.
No anchoring in fairways, over cables, in bathing zones or where an edital forbids it.
Sand or mud; avoid rock, weed and seagrass.
Enough water at low tide; scope from the high-tide depth.
Measure the depth when you arrive and that is enough.
If it is calm now, the bay is a good anchorage.
Practice case & exam keys
Situation
Summer on the west coast. The forecast is nortada, force 5 from the north-north-west, all afternoon. You can anchor in a bay open to the north with a sandy bottom, or in a bay open to the south, behind a headland, with sand patches between rocks. Which do you choose, and what do you check?
Show the answer
The bay open to the south: the headland gives shelter from the north-north-westerly and its swell. In the north-facing bay the shore would be downwind of you, a lee shore. Drop the anchor on a sand patch, never on rock. Check the low-water depth so you stay afloat, work out the chain from the high-water depth, and keep swinging room from the rocks. Read the local edital and any protected-area rules first.
Exam keys
- Shelter from the forecast wind and swell.
- Sand and mud hold well; rock and weed hold badly.
- Low water to stay afloat; high water to calculate the scope.
- Anchor in line with charts, Capitania editais and notices.