I know many doomsday preppers have their bug-out locations hidden away up in the mountains. Maybe something we humans instinctually do is to run for the hills in times of disaster. It also seems reasonable to hide out in rugged mountain location, to make it difficult for others to get to you. But I'd also like you serious preppers to consider the advantages of setting up a bug out spot somewhere near the coast.
Coastal areas are more temperate than inland.
A super-volcano, an asteroid strike, or a nuclear war could all lead to some sort of long-term "winter." Any of these doomsday scenarios could block out the sun, and cause global air temperatures to plummet. But the ocean temperatures stay relatively constant, which helps keeps coastal air temperatures moderate. So while inland temps can drop like a rock, near the beach the ocean adds heat to the air and keeps it warmer. Unless your inland bug out location is getting geothermal heat, you could find things very frigid and nastily cold.
It has been theorized that early North Americans didn't cross a "land bridge" near Alaska, but actually arrived here in small boats. Their little kayaks just followed the clockwise currents from Asia, to North America. If they stayed near land during this trek, they could have caught fish along the way and setup camp on dry land at night.
As a rational prepper, you just may want to entertain the notion that a given doomsday disaster could force you to move to the Southern Hemisphere. Being near the coast gives you the mobility to make that journey the easiest with an extremely efficient mode of travel.
Survival water supplies near the coast
70% of the earth's surface is covered by ocean. Living in California as I do, I can't tell you how much it annoys me hearing government officials mandate water conservation. Just a few miles from where I'm sitting right this second, is a nearly inexhaustible source of water - the Pacific Ocean. If only the nearsighted had build desalination plants here (like Tampa, Fla., like Saudi Arabia, like many other governments), then we wouldn't have to listen to them spew their nonsense about water shortages. It's absolutely true that water produced in this way is about four times as expensive. But really! My water bill is almost nothing, and four times nothing is still nothing. The point being state wide desalination plants would end the water crisis, and wouldn't really cost that much.
As preppers, we can take advantage of all this salt water by desalinating it ourselves. One survival still would meet the drinking / cooking water needs of most families, and the metal pot which holds the sea water could pull double-duty for cooking. This makes for a nice, efficient piece of survival gear that totally meets your water needs.
Food supplies from the Sea
Obviously, barring a mass die off of fish the ocean is packed with food. A fishing pole, or net can bring you ample food to survive doomsday. And with the moderate climate of coastal areas, you find growing food from your heirloom seeds will be much easier. The coastal areas abound with plenty of ways to provide for your survival food needs.
Overall the coasts could be the most feasible spot to make your doomsday bunker. If too close, you could experience a tsunami. But 10 or so miles away from the ocean you should be clear from these rogue waves. You may also find that other survivors eventually get the same idea, making it somewhat populated near the coasts. But if you ensure your defensive capabilities and only make occasional trips to the beach, you should be safe.