Immersion shielding was a deflector shield technology installed aboard the Delta Flyer for use in entering environments with particularly dense atmospheres, such as gas giants or underwater.

This technology was used by members of the USS Voyager crew in 2375, during the Flyer's maiden voyage, in an attempt to retrieve Voyager's multi-spatial probe from the atmosphere of a gas giant in the Delta Quadrant. (VOY: "Extreme Risk")

It was used again later that year when the Flyer was taken to extreme depths of the Waters.(VOY: "Thirty Days")

According to Star Trek Encyclopedia, immersion shielding was a deflector technique employing unimatrix shielding technology.
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