In several cases, people were swimming in areas with strong currents where posted signs warned not to swim there.
In another case, a man was wading in the surf, fishing with friends, and was swept away by a wave.
In all eleven cases, the U.S. Coast Guard was notified and conducted extensive search and rescue operations, but none of the missing were saved.
Petty Officer Steve Lehmann is a public affairs specialist with the Coast Guard's Houston office.
"From Memorial Day Weekend on into summer, we see a lot more people out on the water. And why wouldn't they be? The weather's a lot nicer, it's a lot warmer, people have boats and they want to use them. But one thing they really do need to keep in mind is their personal safety while they're out there."
Lehmann says one simple precaution beachgoers can take is to check weather and sea conditions ahead of time.
"If you go to the National Oceanic Atmospheric Administration website, or NOAA, they have weather conditions, sea conditions. They'll tell you how high to expect the waves to be, the water temperature, these are all important things to know when you're going out on the water or around the water."
According to the World Health Organization, drowning is the third leading cause of accidental death worldwide.