Hi Mike
Operating range particularly with model boats can be very variable, I have sailed models for many years, and in most cases ‘if I can see it I can controle it’. I sail on a lake some 250m long, and don’t have range problems
The position and length of reciever aerial is a important factor (it should not be added to or cut short) and should be positioned well away from electric motors or electronic speed controllers which can give interferance. Ideally the aerial would be mounted outside the structure of the model, as high as possible above the water.
Now we come to the transmitter, the transmitter aerial should not be pointed at the model (radio waves don’t squirt out of the end of the aerial like Harry Potter’s wand
) normally hold the transmitter with the aerial up slightly off vertical. Anything between transmitter and reciever (bushes, trees, Island, water, people) will help reduce the signal.
Finally make sure your batteries are good, and fully charged.
Cheers Tom