The cages are made with nets and are floating in a river.

One thing I forgot to mention is that I am on the other side of the continent so local help would be something that would be greatly appreciated. I wouldn't want to "try" to get something rigged together and would rather have some pointers to a proven solution.

I've got to find a couple of surveillance companies in the area to see what they have to say. However I expect the price to be very high for them to come in to do the job.

Thanks for the suggestions so far.

Rene