The US Navy has a nifty oceangoing research ship which performs a controlled capsize in order to perform scientific tests. It’s called the FLoating Instrument Platform (FLIP), and it was conceived and developed by the Marine Physical Laboratory (MPL) at the Scripps Institution of Oceanography, University of California, San Diego.

FLIP is 355 feet long, and is technically not a ship, but rather a specialized, manned buoy with a 300 foot draft. When in horizontal traveling mode, the long, hollow ballast area trails behind. When it reaches the desired location, the “tail” is flooded until the nose sticks straight up into the air, taking about twenty-eight minutes to reach vertical position. Even in stormy conditions, it is as stable as a fencepost, because most of its length lies in the untroubled waters beneath the waves.

From the FLIP homepage:

During the flip, everyone stands on the outside decks. As FLIP flips, these decks slowly become bulkheads. (This is the name sailors use for walls.) The crew step onto decks that were, only moments before, bulkheads. Inside, decks have become bulkheads; bulkheads have become decks or overheads (ceilings).
Some of FLIP’s furnishings are built so they can rotate to a new position as FLIP flips. Other equipment must be unbolted and moved. Some things, like tables in the galley (kitchen) and sinks in the washroom, are built twice so one is always in the correct position.

FLIP was originally built to measure effects on the environment caused by long range sound propagation, but it has also been used for research in geophysics, meteorology, physical oceanography, non-acoustic anti-submarine warfare, and in laser propagation experiments.

Update, August 2023: FLIP has been officially retired after over 50 years of service.