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" !!!⚡