Inspection cycle:
(1) the external inspection of the bottom of a cargo ship should be carried out at least 2 times in any 5 years, and the interval between any 2 times should not exceed 3 years,
one of them should be carried out during the renewal inspection. The external inspection of the bottom of a passenger ship shall be carried out once every 2 years;
(2) the external inspection of the bottom of a high-speed ship shall generally be carried out once a year;
(3) when the age of the floating dock is more than 10 years, the bottom of the ship shall be inspected at least once every 5 years.
Check Items
(1) hull plate, including the bottom plate, flat keel, side outer plate, bilge keel, head column, tail column and tail frame;
(2) propellers and rudders;
(3) measurement of rudder bearing clearance;
(4) measurement of propeller bearing clearance and inspection of shaft seal device;
(5) submarine valve box, submarine valve, side discharge valve and connection on the hull, as well as the grid at the inlet of seawater.
(6) anchors and anchor chains should be pulled out for inspection, and chain diameter measurement should be carried out if necessary;
(7) hull embalming and painting.
Other Provisions
1. External inspection of the bottom of the ship should generally be carried out in the dock, and underwater inspection can also be used instead of in-dock inspection (except for high-speed ships).
2. When underwater inspection is used instead of in-dock inspection, it shall comply with the provisions  by maritime safety administration.