Check out this drone video of an intake vortex at Lake Texoma:
The video descriptions explains what is causing the vortex:
“Here’s a very unique view of an intake vortex, created as water enters the Denison Dam spillway on Lake Texoma.
The vortex is approximately 8 feet in diameter and capable of sucking in a full-sized boat, so please heed all safety buoys and caution signs.
This is a normal occurrence when flood waters are released from the reservoir via flood control gates.”
Source: usacetulsa via Youtube