The connection between Gen 1:2 and Ps 42:7 exists but is tenuous at best. I note the following:
- There is no connection of context - each verse exists in a quite different context
- Both verses share the word תְּהוֹם = "deep"
- Both share the word עַל = "over"
- Both mention, in different ways, water: Gen 1:2 has water (מַיִם); while Ps 42:7 has waterfalls, waves and billows.
At the same time, there are also differences between these two:
- Gen 1:2 the mood is calm with an expectation of great things about to happen; Ps 42 depicts great turbulence of personal turmoil that the author seeks comfort from God.
- Gen 1:2 the context is darkness and nothing much exists; Ps 42 depicts much action of the created world - day and night pass (V8), water falls over rocks, etc.
- In Gen 1 the focus is the world; Ps 42 the focus is personal.
- In Gen 1 it is God who speaks (and the world is gradually created over 6 days); In Ps 42:7 it is the "deep calling to the deep" that is speaking.
Therefore, while Gen 1:2 and Ps 42:7 share just two words, they appear to be significantly different passages for quite different purposes.