A filter for a shore hole

A filter (18) for a shore hole comprises a substantially square base (19) from which four substantially trapezoidal sidewalls (20) extend upwardly and outwardly to form a substantially square open mouth. Holes (22) are formed in both the base and the sidewalls. In use the filter is supported within a pipe adaptor (11) below a grille (14). The relative sizes of the holes in the filter (18) and the apertures in the grille (14) are such that the filter will trap particles of material small enough to pass through the grille but too large to pass through the filter. The presence of holes (22) in the sidewalls of the filter (18) allow air to escape in conditions of heavy rain.