It's not easy to tell, because it is only a top-down map, but the narrow between the two points is 15 feet above the water on Copper & Stryke's side, and 10-12 feet up on Lorent's side. Terrin quickly will wash through to U30, which is even lower relative to the ridges (the north lake is lower than the south lake by about 10 feet) AND, to make matters worse, the "shore" (as it looks on the map) is a cliff on the west side.
This is all to say: You will quickly run out of rope when it's held at both ends.
But still! I think that we can assume that, being a Rogue, Copper acted quickly. If Terrin can make a dc11 STR Athletics check, thankfully still with Guidance, he can catch the loop of the rope at U32 before washing out to U30. Stryke will drop a Dancing Light down to him, so he doesn't get disadvantage.