uzburkana plitka voda nad pješčanim naslagama, pješčani grebeni, uvjeti se mijenjaju s plimom i osekom i vremenom

wiki/hravatski//Sprudovi nastaju u blizini niskih pješčanih (ili sedimentih) obala, taloženjem tog istog pijeska na neki podvodni greben, zbog djelovanja valova, struja i vjetra.[1]

Sprudovi na ustima morskih i jezerskih zaljeva, imaju tendenciju da se vremenom izdulje cijelom dužinom zaljeva, i nakraju ga potpuno zatvore i pretvore u lagunu.[1]

Duž niskih pješčanih obala, često se formiraju sprudovi u obliku barijera, kao što je to slučaj u Meksičkom zaljevu, gdje su se formirali paralelno s plažama, i pretvorili dobar dio obale u lagune. Oni su isprekidani plimnim uvalama, i povezani podvodnim plimnim deltama. Ti sprudovi pretvoriti su inače krivudavu obalu Meksičkog zaljeva u gotovo ravnu liniju.[1]

Sprudova nema uz stjenovite obale, i tamo gdje je visina plimnog vala viša od dva i pol metra.[1]

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Note added at 19 hrs (2022-05-29 16:32:59 GMT)
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links https://en.wikipedia.org/wiki/Shoal https://hr.wikipedia.org/wiki/Sprud

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Note added at 19 hrs (2022-05-29 16:37:37 GMT)
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https://boatbeat.org/fact-sheets/tips-for-crossing-coastal-b... 1. Evaluate the sea conditions

Do research and establish the tidal period, forecasted weather and sea conditions. The best source for this information is the National Weather Service marine weather forecast and real time sea state data from the NOAA National Data Buoy Center and the NOAA tide and current tables. Determine the times of high and low tide. A boater wants to make the crossing at slack water or during the incoming tide. Take the time to observe the bar conditions checking swell height, period and tidal effects. This can take up to 30 minutes or more.

Coastal bars or inlets having large estuaries can increase the hazard due to the sheer volume of water that has to exit during the tidal exchange. Even during periods where the ocean forecast is favorable the velocity of the outgoing current can make the ***conditions on the bar very treacherous creating short, choppy standing waves known as ebb chop.***

2. Prepare to transit the bar

It’s time to make the go or no-go decision. Before crossing a bar or inlet, inbound or outbound, remain in safe water with good visibility of the entrance. Observe conditions and try to identify the series of larger waves. Measure the amount of time between the series; that is the window to cross the bar. Again, this can take 30 minutes or more. If there are breaking waves, the water looks too rough, there is not enough time to transit the bar area between series, or if the boat operator feels the least bit of hesitation, it’s better to wait. If offshore and the entrance looks too rough to come in, contact the local Coast Guard station.

3. Transit the ***bar ***outbound

Make sure everyone on board is wearing a U.S. Coast Guard-approved life jacket. Secure all loose items; in rough seas they can quickly become dangerous. Have everyone on board remain seated with their weight evenly distributed around the boat. As the boat operator encounters each swell, use only enough power to easily negotiate the incoming waves. Too much power and the boat can launch off the top of the wave, damaging the boat or injuring people. If a breaking wave is encountered, keep the bow into it and apply enough power to make it through.

4. Transit the bar inbound