A ballast water treatment system includes an ultraviolet irradiation device which irradiates ballast water flowing through a treatment line (a pipe) with ultraviolet rays, and a control unit. The ultraviolet irradiation device includes a light source which emits ultraviolet rays, and an illuminance sensor sensing an illuminance of ultraviolet rays received by the ballast water. The control unit controls the ultraviolet irradiation device to maintain at a prescribed dose a dose calculated using an illuminance sensed by the illuminance sensor and a flow rate of ballast water which flows through the ultraviolet irradiation device. When the sensed dose cannot be maintained at the prescribed dose by controlling the ultraviolet irradiation device, the control unit reduces a treatment flow rate of the ballast water which flows through the treatment line.

A pleated filter includes a filter base having folds that repeatedly form mountains and valleys and having a cylindrical shape whose axial direction is a ridge line direction of the folds. The pleated filter includes, in a valley projecting to the inside of the cylindrical shape, a bonded reinforcing portion extending in the ridge line direction of the folds.

A floating construction comprising a container filled fully or partially with water, the lower portion of the container being located within a surrounding body of water and the water surface level of the surrounding body of water being substantially lower than the water surface level inside the container, the container comprising transparent walls or walls with transparent sections and at least one open opening for entering the container, which at least one open opening is located below the surface level of the surrounding body of water, and which floating construction comprises space for spectators observing activities taking place inside the container, wherein the floating construction comprises at least one ballast tank, which ballast tank is connected to the container with a controllable pressure connection, and which ballast tank has controllable water connection to the surrounding body of water.

A floating construction comprising a container filled fully or partially with water, the lower portion of the container being located within a surrounding body of water and the water surface level of the surrounding body of water being substantially lower than the water surface level inside the container, the container comprising transparent walls or walls with transparent sections and at least one open opening for entering the container, which at least one open opening is located below the surface level of the surrounding body of water, and which floating construction comprises space for spectators observing activities taking place inside the container, wherein the floating construction comprises at least one ballast tank, which ballast tank is connected to the container with a controllable pressure connection, and which ballast tank has controllable water connection to the surrounding body of water.

A control unit, a circulation system, and a method for handling ballast water of one or more ballast tanks. The circulation system includes a control unit; a pipe structure having a first system inlet and a first system outlet; and a pump unit for pumping ballast water between the first system inlet and the first system outlet, the pump unit being connected to the control unit. The control unit is configured to: obtain a volume parameter indicative of pumped volume; determine if a pump criterion is fulfilled, the pump criterion being based on the volume parameter; and operate the pump unit based on whether the pump criterion is fulfilled or not.

A marine thru-hull fitting drainage device directs fluid away from a thru-hull fitting in the hull of a vessel. The drainage device includes a resiliently flexible channel body having a substantially U-shaped cross-sectional area, the body shaped to taper from a first flat end proximate to the hull of the vessel to a second narrower end that is distal from the hull of the vessel. The device also includes a flange attached to the first end of the body proximate to the hull having a flat surface area shaped to conform around an edge of the thru-hull fitting on the hull of the boat and an adhesive material formed on the flat surface area of the semi-circular flange, the adhesive material attached to the flat surface area of the semi-circular flange on a first side and having a removable non-adhesive layer concealing a second adhesive side of the adhesive material.

A marine thru-hull fitting drainage device directs fluid away from a thru-hull fitting in the hull of a vessel. The drainage device includes a resiliently flexible channel body having a substantially U-shaped cross-sectional area, the body shaped to taper from a first flat end proximate to the hull of the vessel to a second narrower end that is distal from the hull of the vessel. The device also includes a flange attached to the first end of the body proximate to the hull having a flat surface area shaped to conform around an edge of the thru-hull fitting on the hull of the boat and an adhesive material formed on the flat surface area of the semi-circular flange, the adhesive material attached to the flat surface area of the semi-circular flange on a first side and having a removable non-adhesive layer concealing a second adhesive side of the adhesive material.

A method for energy generation includes receiving, at a carbon negative energy generation system, input including calcium oxide and water and reacting, within a reaction chamber of the carbon negative energy generation system, the calcium oxide and water to release energy and generate calcium hydroxide. The method further includes directing, by the carbon negative energy generation system, the released energy to facilitate propulsion or onboard electricity generation and dispensing, by the carbon negative energy generation system, the calcium hydroxide into the ocean to sequester atmospheric CO.sub.2.

A personal watercraft includes a watercraft body including: a center elongated protrusion located at a center of the watercraft body in a left-right direction, extending in a front-rear direction, and having an upwardly convex cross-sectional shape; a drainage channel outward of and adjacent to the center elongated protrusion in the left-right direction, lying along the center elongated protrusion in the front-rear direction, extending rearward and outward in the left-right direction, and having a downwardly convex cross-sectional shape; and an outside elongated protrusion outward of and adjacent to the drainage channel in the left-right direction, lying along the drainage channel in the front-rear direction, having an upwardly convex cross-sectional shape, and facing the drainage channel from outside in the left-right direction.

A personal watercraft includes a watercraft body including: a center elongated protrusion located at a center of the watercraft body in a left-right direction, extending in a front-rear direction, and having an upwardly convex cross-sectional shape; a drainage channel outward of and adjacent to the center elongated protrusion in the left-right direction, lying along the center elongated protrusion in the front-rear direction, extending rearward and outward in the left-right direction, and having a downwardly convex cross-sectional shape; and an outside elongated protrusion outward of and adjacent to the drainage channel in the left-right direction, lying along the drainage channel in the front-rear direction, having an upwardly convex cross-sectional shape, and facing the drainage channel from outside in the left-right direction.