K-21 Amphibious Infantry Fighting Vehicle not so Amphibious.

Defense News is reporting that a design flaw has been found in the K-21.

"An armored vehicle weighing 25 tons or more is required to maintain at least 20 percent of reserve buoyancy when it crosses the river, but the K2 has been found not to meet that requirement," Kim said, citing the results of a two-month probe of the accidents.
The front of the vehicle, where crew members were on board, became heavier than the rear section, allowing water to flow into the air intake hose of the engine, he said.
The investigation revealed that the spread of the vehicle's weight is unbalanced, with 54.2 percent of the total weight in the front part, said the minister.
The height of the wave plate also is found to be shorter than the requirement, he noted. The plate was required to be 22 centimeters high under the original design requirement, but the manufacturer changed the design in consultations with the Defense Agency for Technology and Quality (DTaQ).
As a result, the plate's height was designed to become 7 to 11 centimeters.
There also was a problem with the drain pump, according to the investigation. When the vehicle moves at full speed, the pressure inside the engine compartment goes down, so more water flows into the compartment. But the pump fails to adequately remove the water.

Designing an amphibious fighting vehicle is alot tougher than many realize.  The K-21 was once touted by some to be a contender to replace the AAV in the USMC.  I never took that talk seriously and the unfortunate deaths and the findings of this study bear that out.