Shallow Water Anchoring

[sailorboy1]

Lets say the anchorage you what to explore is shallow with soft bottom. How shallow are you willing to anchor in in calm conditions (low bouncing), lets say your draft is 6 foot?

[gettinthere]

overnight in an unknown place or for a lunch stop?

Brief stop in familiar territory, 2' below the keel.
Overnight in a less well known spot, 4' below the keel.

I've not anchored in high tidal areas, not sure how I might change that...

[daddle]

My draft is 8 feet. I've anchored where the depth at low tide was only 5 or 6 feet. Very soft slough-bottom mud. No ill effects. Not much rocking at low tide either.

[cfarrar]

Soft Chesapeake mud? Zero ft is fine under the keel.

Bahamas Sand? 1-2 feet, in nice weather.

Down East with a 14 ft tide and rock ledges? Calculate conservatively the threat posed by the various ledges at low tide, and give yourself plenty of horizontal separation.

[Vasco]

Depends on whether the anchorage is sheltered or not. If there's a lot of fetch I like at least 2 feet under the keel at low water. If it's sheltered about half a foot will do me. Also make sure the bottom is uniform in depth, no humps you can swing into.

[Arch Stanton]

Originally Posted by gettinthere

I've not anchored in high tidal areas, not sure how I might change that...

The 18' tides here in the Puget Sound make it tricky sometimes. Swinging 180° around an anchor with proper rode along a sloped bottom as the tide goes out can easily change your clearance from over 30' to less than 5' in a couple hours.

You have to either be really picky and patient about anchorages, or get up every couple hours to check things.

[mrohr]

Had a steel boat,never worried about such details; got some good stories with such a cavlier attitude . Like to keep a couple of feet above the bottom at low water now that I have fiberglass. Still not afraid of sitting in mud when in a VERY protected spot , but don't believe it's smart seamanship.

[Pete7]

Originally Posted by gettinthere

overnight in an unknown place or for a lunch stop? Brief stop in familiar territory, 2' below the keel. Overnight in a less well known spot, 4' below the keel. I've not anchored in high tidal areas, not sure how I might change that...

You have a choice, either some maths involving time and the rule of twelves on the back of a cigarette packet or buy a yacht with two keels and pretend you meant to dry out there

Don, with a 4 foot draft we will happily anchor in 5 foot if we know the bottom is flat and either sand or mud. However, if the there is a chance of an uneven bottom or rock, then we would be more cautious. The steel keels I don't worry about, but the rudder whilst a few inches less depth is GRP.

Pete



Pete

[klem]

In areas with lots of tide, I always shoot for at least 5'. The reason that I leave so much is that calculating what the water depth at low water should be is far from an exact science and there are often rocks or other things around. The water tends to be murky so you can't see if your depth sounder has found the shallowest spot.

In places with clear water, flat bottoms and less tide, obviously much less is appropriate. Boy was it a shock the first time I cruised in the Bahamas though.

[MichaelC]

There are, as the saying goes, bold sailors and old sailors, but damn few old, bold sailors. Your chart shows depth at mean low water. Make sure you have 2 ft more than your draft, unless you plan to beach her to clean her. Most fin keel boats do not do well with this. Scope, however - be sure you have 4 to 1 minimum at HIGH water. Incidentally, Puget sound tides are maximum 12 foot range, normal is 7 to 9 feet, depending on the time of year. That is from low to high.

[senormechanico]

Olympia is at the very South end of Puget sound and the tides get a lot bigger than up North. We get 7 to 9 here on Whidbey. Seattle is more, and Oly gets the most.

[boatman61]

Once again... MLWS info of the chart plus 1metre... depending on tidal range.. sometimes a bit deeper.

[zeehag]

west coast usa-- my 6'6 plus 10 ft. anywhere else-- prolly same-- give me a better chance to get my but out of trouble if needed.....boat is waaay huge under water...

[sailorboy1]

Guess I wasn't clear. Assume we are talking about being at that anchorage during low tide. What I was really trying to ask was how much less at low tide than your draft would you be willing to anchor in calm conditions.

heck in my normal area I could anchor at high tide and have 3+ feet clearance but be fully out of the water at low tide.

[daddle]

I've seen goofballs anchor in 10 feet of water, 4 feet to spare, at La Cruz de Huanacaxtle, calm mexican conditions, then a set of breakers rolls in without warning. Heh. Almost funny.

So it depends.