As Greg mentioned above, we had a similar challenge. Luckily for you, I am currently a beach bum and I can be unbiased.
As with any Video Based technology I suggest setting the expectations first:
1- Especially frequent in marine environment in CA, the marine layer, prevalent throughout the spring (May grey, June gloom..) will make any camera system useless.
2- In order to successfully establish virtual rules, the physical rules have to be defined. In my specific case, the exact azimuth/point at which a kayaks became a threat had to be defined since the lagoon was partially public and was used as an oyster farm. Thus, it is easier to establish low False Alarm Rate and High Probability of detection when the main asset is defined. this could be, the shore line, a pump, an intake, etc.
3- Video Analytics works best with X axis motion Vs. Y axis. in other words, speed and accuracy is better with motion across the Field of View and not toward or away from the camera. In my case there was no physical way to mount the cameras that way, so we mounted the cameras very high, at 90 Feet!
4- As the Video Monitoring outfits out there can attest, Video Analytics can NOT replace the human guard. The final decision on a possible threat has to be made by human. In my project I used a dual, fixed to PTZ rules where the PTZ would automatically "slew to cue" to minimize the team workload.
If this did not deter you from the VA solution, I suggest the following:
Contact a few of the leading companies that specialize in VA. You can contact me directly for suggestions.
let them compete on the project. It is their job to provide you with a free pilot demo product for a set time. If they are serious, they will also offer support in setting up the rules.. In my 10 years of specifying Video Analytics I never shied away from an opportunity to establish my product superiority ;)
In return you can offer them (beyond the sale $$$) a write-up, case study or any sort of public recognition.
Minimizing the false alarms is a process that will take some time. The rules will need to be tweaked a few times.
Hope this helps.