wade through treacle – to make one’s way slowly or laboriously. See [wade through] and [treacle]

A colleague used it as an example to explain English is such a tricky language. He was once talking to some non-native English speakers and used the expression “wade through treacle” , but found no one understood it.  In fact, once you know what treacle is, the meaning of this phrase is very intuitive – Just think of yourself walking in syrup.