The special shows an incident of a manatee being hit by boat propeller. There is an individual in the NPS with Big Cypress who claims airboats can injure manatees in the Stairsteps unit of Big Cypress National Park. I don't think this is possible. Airboats are less likely to injure manatees than boats with props. It is possible for an airboat to hit a manatee and for injury or death to result from the collision.
Many manatees die from internal injuries sustained when hit by the hull of boats including airboats.
But the manatee and the airboat must be in a place where both are found. When airboats are running in a few inches of water, it is unlikely they will encounter a manatee. The amount of money proposed to fund restoration is the result of a multi-year study by biologists, hydrologists, engineers, and others. It represents the best estimate we have at the cost of restoring a good flow of water through the Everglades. This will enable the building of reservoirs, stormwater treatment areas, the backfilling of canals, and other projects.