Speedo had the first buoyancy suit used in the 2008 summer olympics, but then other manufacturers went them one better creating suits that had the buoyancy material throughout the entire suit and those companies took over the swimming world in 2009. In 2009 so many world records were set (and yes, some swimmers wore mutiple suits in order to increase buoyancy even more) that the INTERNATIONAL body (FINA) ended up banning the suits.
At that time FINA implemented an approval rule requiring all suits to be submitted to FINA for certification (that they were "textile only") before they could be permitted to be used in competition.
Unfortunately, certain body types and certain strokes benefited most from the buoyancy suits, so they were not even an "equally beneficial" enhancement.
Again, it required the International body to make the ruling that returned "integrity" to the sport of swimming. Sorry to say, FINA was never ethical enough to declare the "buoyancy records" invalid, nor even add an asterisk to those times. If you watch swimming championships on television or the internet you will sometimes hear the announcers reference a swim as "the fastest textile swim ever." However, ANY swim record that still exists from 2008 or 2009 is an artificially enhanced record.
IAAF needs to step up and make a decision to require a similar "approval certification" rule to prevent distance running from being inundated with false records.