shaker assemblies comprising rigid element 11 baseplate 12 and shaker unit 13 to be brought completely out of the water as shown in fig3 for maintenance and for transiting to the work site a cross section of the raised shaker assemblies within the twin hulls is presented in fig4 a similar benefit could be accomplished with an outrigger structure extending along the sides of the vessel 1 where the shaker and baseplate assemblies could be raised at the sides of the vessel 1 at least partially into the outrigger structure the outrigger structure with attached raised shaker baseplate assemblies preferably would not extend below the waterline to present unnecessary water drag when transiting such a structure would add significant weight to the vessel 1 which may have to be accounted for in overall vessel design such is not shown but is within the skill of the ordinary off shore vessel construction company to avoid damaging the water bottom and to maintain very low ground pressure each baseplate 12 preferably has a large area the area of the baseplate 12 is sized to generate a very low effective ground pressure preferably on the order of 1 to 3 psi 6 9 to 20 7 kpa or lower thus ranges of size in width and length can typically be from 500 cm to 300 cm preferably from 400 cm to 800 cm and most preferably at least 500 cm to at least 400 cm but will depend largely upon the size of the vessel 1 and the type of water bottom 14.