If the arrest was recent
Start with the county jail
Someone just arrested in Florida is almost always in a COUNTY JAIL run by that county's sheriff, not in the state prison system.
Most Florida sheriffs publish an online jail roster or 'arrest inquiry / who's in custody' search for their own county, so pick the county where the arrest happened.
VINELink covers Florida statewide across participating jails and is the fastest single check when you don't know the county.
County jail rosters are fragmented across Florida's 67 county sheriffs; there is no single statewide county-jail search, so identify the arresting county's sheriff roster or use VINELink.