You may perhaps want to plan for an alternate (not due to weather) when flying offshore (pointing out over the big blue);
- conducting MPT (and you cannot find and/or see the vessel)
- tracking to an offshore pontoon/helipad and you cannot find/see it or it has sunk or drifted away
- an aircraft malfunction necessitating a return to base (or alternate HLS)
You could think of an "Alternate" as another way of saying
backup plan! 
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