Removing hazards: We all try to do beach cleanup e.g. identify hazards such as sharp metal, and organize regular (often daily) beach cleanups.
There are great health benefits to cold-water swimming, but we also are mindful of safety, e.g. easing into the water slowly and putting the face (vasovagal response) and head in the water only once adjusted to the cold, and also we often wear a swim cap to maintain congnitive capacity to think clearly.
Dealing with hooligans:
Most people are friendly, but for safety, swim in groups, don't leave valuables on the beach, etc..
Most dogs are friedly, but in general, we try to avoid leaving food out in the open, e.g. we put food in our towfloats or sealed away until consumed.
Most security guards are well-meaning and may simply warn of hazards. However, if a security guard oversteps the authority and enters into the realm of illegal behavour it is best to have a group response:
Dealing with overzealous or unlawful security guards:
What we usually do is start recording and live-streaming (so they can't seize or destroy evidence). Then they will demand that we stop recording. We often ask others around us to start recording and live-streaming also. If you have 5 or 6 people recording them, you explain to them that you are collecting evidence for use in court and that if they try to destroy or stop any of the recordings that they are guilty of destruction of evidence.
Most of the time this will make them cease their illegal behaviour.
If belligerence persists, once we are all recording, we ask them to show identification, i.e. to prove that they have authority over us.
Also we believe that the lake is federal property (Canada) so we believe that if they demand you exit the lake that they are demanding that you leave Canada and cross the border into Ontario, and therefore this would be false imprisonment which we believe is a crime. When we believe a crime is being committed we think we all have a responsibility to record the crime-in-progress and to also get good clear closeup photographs of the perpetrators so that they can be brought to justice.
Hopefully, though, it doesn't reach this level, and we can de-escalate at an early stage of development.
Technology for safety: We use various recording and transmitting technologies to ensure safety, e.g. live-streaming as mentioned above, GPS logger and transmitter, swim-path transmitted live, underwater seeing aid, overhead seeing aid, mapping of hazards for avoidance and removal, water condition monitors, etc..
See also, SafeSwim IEEE Conference Presentation SafeSwim: Overhead vision to help people see better
Safety first. Safety in numbers.