Hi Nick
The standard supplied aerial will be suitable for most surface models provided it is above the waterline and not shielded by metal or carbon fibre plates or tubes.
The actual aerial is the small exposed length of wire at the very tip and this is enclosed in a coaxial cable. Both wires are attached to the circuit board sometimes by a removeable connector.
Many moons ago in the days of 27Mhz we used to attach the rx aerials to bits of wire often attached to the masts or aerials etc and this hid the long length of black aerial wire from view.
The modern shorter wire is easily hidden in the superstructure and even two wires are not a problem. Unlike flying models the need to place the aerials at 90deg is not strictly necessary in a model boat or car as they remain in the same horizontal plain unlike a model plane or drone.
This applies to all radio sets operating in the 2.4Ghz band.
dave976

The ghz antenna is above the round lump. It’s cut to frequency As I see two lay one horizontal n one as vertical as you can. Range in that frequency is usually good. Keep it away from metal. Like don’t put in a metal tube. I wouldn’t fool with it. Spektrum has one fir gliders that has a longer lead from any to radio. Once you set up radio try a distance test to see how far you get reliably. You should be fine in a pond. If boat is too far away you can’t tell its direction anyway. As long as the horizontal is above waterline n vertical even at 45 deg it will give great reception. I use sane radio on aircraft and can fly to where it’s not visible I then can use FFP a camera in plane. Try with a ship?

A longer antenna will not necessarily ensure better performance in the microwave frequency bands, that is, bands above 960MHz.

At microwave frequency not always "more wire is better". Down on the LF, MF, & HF bands that is usually true, that the more wire on the receiver, the better the clarity of the received signal.

I just re-read your original question & your rationale for doing so. Just go ahead & add the wire that you require to reach. Then do a range check over land. If it works reliably to the distance that you require to operate, then I wud say that you are good to go.

You might get slightly better signal operating across water. But doing a range check on a lake is risky, so do it in an open field.

Please let us know what you do, & experience, in the end. Radio doesn't always follow science, sometimes "Radio is magic" !!!⚡

I do not know about FlySky, but FrSky has diffent length antennas that can be installed. That said, the antennas are still tuned to the particular frequency.
I might suggest inquiring on a site that has a specific section dedicated to radios, something like RC Groups. You might also look for a FlySky specific forum, perhaps on a dealer web site.
Sorry I can't be more helpful.

My understanding of these aerials is that the length is the optimum. Any change in length could lead to poorer reception.
I'm afraid I don't know the technicalities of this - perhaps someone else could help ? 😉

Can I make the lead I have longer or is the lead that is fitted to the receiver calibrated to the operating frequency, I would like if possible make the antenna 4x longer to be able to connect it to a telescopic Aries.🤔

Nick, I can only surmise that you need to reinstate the receiver leads, or that you have a receiver model I am not familiar with. I use the FS-iA6B and lead dimensions can be gathered from the attached photo.
Hope this helps😉