Michelle Wittmann sent a series of pictures of the manatee under water to the The Texas Marine Mammal Stranding Network.
She says it was her son, Andrew, who made the discovery.
"Thanks to Michelle and Andrew Wittmann for this report and photo!," wrote the network on its Facebook page.
The TMMSN works with the U.S. Fish and Wildlife Service to monitor manatees in Texas waters. They say they don't normally see manatees every day.
They ask anyone who spots a manatee to call 1-800-9MAMMAL.
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