this is a little bit confusing to me. Assuming that we are talking about a repeater (duplex) channel?. Then isn’t the RX transmission from the boat 2km away, likely to be coming from the same repeater as the coast based transmissions? In this case I’d expect that the coast based transmission to be better on the whole as they are likely to get a stronger transmission between their antenna and the repeater than the boat offshore would (all else being equal as far as antenna length and power output of the radios themselves of course).
if we are talking about a basic simplex transmission then this makes sense and please disregard.