Basically, the only thing that you should be concerned about getting water into under your Hood
is your Intake
Although the following items are already waterproof, you should check the tightness of the oil filler cap, the power steering filler cap, windshield washer fluid cap, oil dip stick, battery filler caps and all other engine compartment opening caps.
everything else should be fine... there really isnt much under your Hood
that isnt already water proof.