Possible Clues:

• Aquatic creature�s driven one from river not stable
• Frail aquatic creature seen between banks of Tay?
• ...and again, in a wobbly condition
• What the adder might do, perhaps, in an unsteady way
• Staggering - like the salvage collectors?
• Unstable
• Unsteady toddler, crying, losing heart
• Like a summer, as it were, that's unfit for steady walks?
• Walking shakily
• Likely to rock