 ‘between the rocks’ can modify the event of floating, saying where it happened and thus acts as an adjunct. It can also act as an argument of ‘float’, specifying where the resulting location of the boat on account of the floating. It can also act as an adjunct modifying ‘the boat’, helping to specify which boat it is. All of these are readings of (1) and in each case we find ‘between the rocks’ playing very different roles. Assuming these roles are dictated by their relations in the relevant LF, we get three very different LFs that correspond to (1).