If you have 6 hours or a half day to spend in Banff, there are plenty of things to do. Here are some suggestions:
1. Visit Duff House - a beautiful Georgian mansion housing art exhibitions. Allow 1-2 hours for the visit.
2. Walk around Banff Marina - a picturesque harbor area with views of the seacoast. Allow 30-60 minutes for the walk.
3. Explore Banff Castle - a ruined castle with a rich history. Allow 1-2 hours for the visit.
4. Go to Macduff Marine Aquarium - a small aquarium showcasing marine life in the region. Allow 1-2 hours for the visit.
5. Have a meal or a drink in one of the local restaurants or pubs. Allow 1-2 hours for the meal or drink.
Overall, you could do all of these activities in 6 hours or less, depending on your pace. Keep in mind that some of these activities may have limited opening hours or may require an admission fee, so plan accordingly.