When my students ask for recommendations, for weekend activities, I often remind them that Dublin is on a bay, and encourage them to take advantage of that fact, every weekend or evening when the weather is good enough.
The South Bull Wall, above.
North (Bull) Wall; above. With Bull Island alongside.
West Pier, Dun Laoghaire. above.
I hope to post on Colliemore Harbour again soon. But in the meanwhile, two bits of suggested further reading for you. First, for what I think is the best route for walking around Howth Head, you could see my post “From Sea to Shining Sea”, link: Sea to Shining Sea