Marine biologists detected DNA from the rare comb jelly in samples taken inside Harrow Lagoon, although repeated net surveys there found none. The same genetic variants were abundant in the offshore cove. Laboratory tests show that the jelly's free DNA remains detectable in seawater for at least eighteen hours. During each of the two days before sampling, a flood tide carried water from the cove through the lagoon's narrow inlet; drifters traversed that distance in under four hours. On ebb tides, water left by a different channel. Thus the lagoon samples contained biological material associated with the jelly, but the sampling method did not reveal whether intact jellies produced it within the lagoon.