Trips/things to do in Reykjavik

[Butterbeer]

I went to Iceland about 5 years ago with a group of friends. Two of the things we really enjoyed if you like to learn a little about the history/culture of places were a comedy show called How to Become Icelandic in 60 minutes (incredibly funny but we actually learnt a bit too!) and we also enjoyed the brewery tour, which went in to the history of alcohol in Iceland a bit, was also quite funny, and include a fair few beers! We also went on a guided tour in to a lava cave, which was amazing. That was roughly half a day, we were picked up and dropped off at our accommodation

[smary]

Does anyone know how much whale watching would be to book on the day in Reykjavik? Or is it cheaper to book online?

I've seen a few deals for around 60-70GBP to book for Easter Sunday but unsure whether it's cheaper to book when I'm there?