Slack tide is the turning point when a body of tidal water can seem uncertain as to whether it is coming in or going out. While surface water may be deceptively calm at this time, below the surface huge divergent forces are at work. In the title of Sarah Day’s ninth collection the term is an expression of twenty-first century unease. World events and global forces are an oblique presence in much of this collection in whose poems private and public disturb one another’s space and boundaries. While the themes often hold considerable gravitas, there is playfulness and whimsy too, in tone, voice, and angle of approach. These poems seek what Robert Pinsky called ‘a collaboration between the external world and the self, between language and intention’.