I was there March 3 and seen one. Theres no guarantee that you will see one any time of the year, but generally if it's cooler you have a better chance of seeing them.
Was there 2 wks ago. Manatees we're in the park area, but not visible due to brackish water.
My husband and I visited last March and manatees were not in the river or park pool. Don't waste your time unless you're going to rent a canoe or hike around the grounds.
Thanks! Your answer is awaiting moderation.