The pair, stuck in knee-deep mud, were spotted by Marcelo Clavijo and several others visiting a local bay to see the effects of Irma.
Clavejo said the rescue was a "pretty cool experience" and he was happy to rescue two of "manatees finest".
A line of evacuees wait for food at the Braden River High School emergency shelter
The deputies, which had no special training, "just used common sense", Bristow says. "They are really heavy". As Irma approaches, the offshore winds, moving counter-clockwise, push the water out.
"Under normal circumstances, they would never beach themselves voluntarily, so it's an animal that could be compromised by a situation like this", Jack Cover, general curator at the National Aquarium in Baltimore, tells NPR. "We couldn't just let those manatees die out there".
An official with the Florida Fish & Wildlife Conservation Commission said the organization received multiple reports about the stranded manatees. "Unfortunately with manatees, they are accustomed to being tidally stranded at times".
It's a phenomenon sometimes called "hurricane bulge".