John Gill Commentary Psalms 42:7

"Deep calleth unto deep at the noise of thy waterfalls: All thy waves and thy billows are gone over me." — Psalms 42:7 (ASV)

Deep calleth unto deep at the noise of the water spouts
By which are meant afflictions, comparable to the deep waters of the sea, for their multitude and overwhelming nature; see (Psalms 69:1Psalms 69:2) (Isaiah 43:2) ; these came pouring down, one after another, upon the psalmist: as soon as one affliction over, another came, as in the case of Job; which is signified by one calling to another, and were clamorous, troublesome, and very grievous and distressing;

all thy waves and thy billows are gone over me :
with which he seemed to be covered and overwhelmed, as a ship is at sea. It may be observed, that the psalmist calls afflictions God's water spouts, and "his" waves and "his" billows; because they are appointed, sent, ordered, and overruled by him, and made to work for the good of his people: and now, though these might seem to be a just cause of dejection, yet they were not, as appears from (Psalms 42:8) .