As the controller needs to be central and to transmitt data over water I assume from your description then your best option would be a radio network on the ISM(Industrial,scientific,medical) band187,214,233,900Mhz and 2.4Ghz.Token ring isnt a good topography for your application but a simple collision detect random backoff (alloa)network would be more suitable.
There are lots of suitable radio transceiver chips available to do the radio stage.