An inflatable flood defence structural unit is described for creating an inflatable flood defence arrangement. The unit comprises at least one inflatable chamber comprising a front wall and a rear wall which extend in a substantially parallel orientation. At least one of the front and rear walls provide a water barrier, and a first and second end wall are arranged to couple the front and rear walls together at a respective first and second end of the front and rear walls. The unit further comprises a first inflatable buttress which is rigidly bonded at a proximal end thereof to the rear wall of the chamber, proximate the first end of the chamber and which extends in a direction which is away from the chamber, and a second inflatable buttress which is rigidly bonded at a proximal end thereof to the rear wall of the chamber, proximate the second end of the chamber, and which similarly extends in a direction which is away from the chamber. The unit further comprises a fastening arrangement disposed upon at least one of the first or second buttress for fastening the first and second buttress to a second and first buttress respectively, of a further structural unit to create the flood defence arrangement.