Rashi on Exodus 15:10/רש"י על שמות ט״ו:י׳

1נשפת — an expression for “blowing”. Similar is (Isaiah 40:24) “He bloweth (נשף) upon them”.

2צללו means THEY SANK, they went deep, — an expression of the same root as (Psalms 69:3) מצולה “the depths”.

3כעופרת LIKE LEAD: old French plomb.