In-water survey

In-water survey (referred to by various classification societies as IWS, BIS, etc.) is a method of surveying the underwater parts of a ship while it is still afloat instead of having to dry-dock it for examination of these areas as was conventionally done.
For cargo ships, two surveys are required within a period of five years. One of these can be an in-water survey, provided the ship is eligible for it.