Both the crashing, splashing of waves or waterfalls and forests (especially pine trees) emit negative ions. Negative ions deter depression or the blues. Therefore, negative ions actually uplift your mood. That’s why even if you are grieving, sitting on a beach or hiking in the woods soothes your soul.
Personally, I need the stillness I find by a mountain lake surrounded by trees. The beach is alive with noisy commotion and sometimes stirs me up, albeit positively. But a forest full of conifers alive with birds, squirrels and chipmunks dining on nuts and seeds, instills an innocent serenity I treasure.