In 2006, we wrote about an application in which low-frequency (LF) tags placed on pipelines were read underwater using a handheld reader (see Taking RFID to New Depths). However, it appears that the company that made the system, Enertag, has since gone under (so to speak), as its Web site is no longer active.
There are businesses that manufacture tags that can be read underwater. Technologies ROI (TROI) makes tags that it claims can survive depths of 1 mile underwater (see Armored-RFID Tag Loves to Get Hammered). Omni-ID produces tags that can be read while submerged in water as well.
That said, these tags must be read at fairly close range. I do not believe it is possible to read, from the surface, even an active tag submerged under 400 meters of water.
—Mark Roberti, Editor, RFID Journal
Is It Worth Using RFID to Track Shipping Containers? »