The present invention is a method of suppressing bio-film formation on a structure in water, including irradiating light comprising the spectrum of 409 to 412 nm to the structure where bio-film formation is to be suppressed.

A drainage device for directing fluid away from a thru-hull fitting located on a hull of a vessel includes: a channel body mountable proximate to and extendable away from the hull of the vessel; a groove formed along at least a partial length of the thru-hull body; and a lip protruding from a bottom edge of the channel body at an end of the channel body that is distal from the hull of the vessel when the drainage device is mounted thereon.

A drainage device for directing fluid away from a thru-hull fitting located on a hull of a vessel includes: a channel body mountable proximate to and extendable away from the hull of the vessel; a groove formed along at least a partial length of the thru-hull body; and a lip protruding from a bottom edge of the channel body at an end of the channel body that is distal from the hull of the vessel when the drainage device is mounted thereon.

A bio-fouling transducer comprising: a housing comprising: a diaphragm a conduit attached to the diaphragm; and a cap attached to the conduit; a transducer element attached to the diaphragm within the conduit; a series of electrical connections electrically connected to the transducer; and at least one gasket attached to the transducer and in contact with the conduit.

A bio-fouling transducer comprising: a housing comprising: a diaphragm a conduit attached to the diaphragm; and a cap attached to the conduit; a transducer element attached to the diaphragm within the conduit; a series of electrical connections electrically connected to the transducer; and at least one gasket attached to the transducer and in contact with the conduit.

The invention discloses a method for preparing an anticorrosive surface layer of a metal material in a marine environment by laser, which belongs to the technical field of laser processing. First, the laser cladding method is used to prepare a cladding surface layer on the surface of the metal material that is not easy to undergo chemical substitution reaction with the chlorides (NaCl, MgCl.sub.2 , CaCl.sub.2 etc.) in the seawater. Then, on the surface of the cladding surface layer, ultrafast laser processing is used to form a surface layer with a wetting angle (and water) greater than 90 degrees and with hydrophobic characteristics. The anti-corrosion surface layer obtained by the invention has hydrophobic properties, the high humidity and high salt water vapor and marine organisms in the marine environment are not easy to adhere, and the anti-corrosion surface layer is stable in salt water resistance, and is not easy to undergo chemical substitution reaction with chlorides in seawater (NaCl, MgCl.sub.2 , CaCl.sub.2 etc.), which can achieve high-efficiency anti-corrosion of metal materials in the marine environment.

The invention discloses a method for preparing an anticorrosive surface layer of a metal material in a marine environment by laser, which belongs to the technical field of laser processing. First, the laser cladding method is used to prepare a cladding surface layer on the surface of the metal material that is not easy to undergo chemical substitution reaction with the chlorides (NaCl, MgCl.sub.2 , CaCl.sub.2 etc.) in the seawater. Then, on the surface of the cladding surface layer, ultrafast laser processing is used to form a surface layer with a wetting angle (and water) greater than 90 degrees and with hydrophobic characteristics. The anti-corrosion surface layer obtained by the invention has hydrophobic properties, the high humidity and high salt water vapor and marine organisms in the marine environment are not easy to adhere, and the anti-corrosion surface layer is stable in salt water resistance, and is not easy to undergo chemical substitution reaction with chlorides in seawater (NaCl, MgCl.sub.2 , CaCl.sub.2 etc.), which can achieve high-efficiency anti-corrosion of metal materials in the marine environment.

There is provided a casing for a towable sonar apparatus, comprising: a tubular member, wherein the tubular member comprises a foam member or a mesh member; a first layer around the tubular member, wherein the first layer is porous.

There is provided a casing for a towable sonar apparatus, comprising: a tubular member, wherein the tubular member comprises a foam member or a mesh member; a first layer around the tubular member, wherein the first layer is porous.

The invention provides a light guide element comprising a light guide and a layer element, wherein the light guide comprises a light guide face and wherein the layer element comprises an optical layer, wherein said optical layer is in contact with at least part of the light guide face, wherein the optical layer has a first index of refraction (n1) smaller than the refractive index of seawater, wherein the light guide comprises a UV radiation transmissive light guide material.