HM Coastguard's advice for people who become stuck in mud is to stay calm and try to spread their weight as much as possible.
A spokesperson said: "People can find themselves in soft ground either when the surface is so soft that they simply sink to a point where movement becomes impossible, or they break through a layer of relatively firm mud into a soft bubble described above.
"Invariably, with quicksand there is generally little or no warning of transition from firm sand to quicksand.
"People can also require rescue as a result of exhaustion while trying to wade through soft ground for all they may not be trapped. In all cases, the casualty may be at risk from incoming tide.
"The effect in both cases is that when the person tries to pull their legs free they create a vacuum underneath their feet and around the leg which prevents escape and further movement can make the situation worse.
"One immediate measure that can be taken to prevent the casualty sinking further is to sit on the surface of the mud/quicksand, thus spreading the load and may reduce further risk to injured casualties."