We have some of our APs around 200m from the ocean - 72s and 74s. No issues here other than they start to look pretty terrible after a year (but that isn't Meraki's fault). They have survived rain, moisture, birds, etc.
Be sure to properly ground them, it isn't just for lightning strikes!
Good point about grounding. Can you share any tips or best practices you implement. The Installation guide is weak in my opinion. I usually attached the Green grounding strap to the AP ground lug. I then run a ground from the same lug to ground using 14 gauge or better wire.
Would using Shielded and properly grounded ethernet runs suffice or do you always have to ground the AP with a separate wire?