The values which could be Janice's depth are 42, 39 and 61.
The Breakdown
If Peter is scuba diving at -35 feet below sea level, Janice's depth could be any value that is deeper than Peter's depth.
Therefore,
-19 feet is shallower than peter
-34 feet is shallower than Peter
-25 feet is shallower than Peter
-42 feet is deeper than Peter
-39 feet is deeper than Peter
-61 feet is deeper than Peter.
So the depths that are below Peter are 42, 39, 61. Janice could be in any of those levels.