Ads like that will appear because the content of the page (i.e. the posts) refer to dolphins or swimming with dolphins. Google very cleverly matches advertisers to the page content. You don't actually get asked if you are happy with each one but you do have full control to prevent any advert reappearing.
The other important point is that 2 people reading the same page at the same time are unlikely to be seeing the same Google adverts - so there can be adverts that I simply haven't seen yet but other people have - in these situations if it is something a little tactless I'd appreciate a quick email with the website address concerned. As I said last night, I removed the swimming with dolphins company from acceptable adverts but even now haven't personally seen it
One example is adverts for Israel appearing on pages where diving is being discussed. You can follow the logic of that but also can't expect Google to realise that at this time it is not tactful or desired on a forum about Turkey.