We have one who rarely fails to show for the Advanced Powerboat Courses that we run out of the Aran Islands in Galway Bay.
A few years ago while in one of the Army RIBs this dolphin stayed with us at 35 knots for 5 minutes....incredible speed and endurance.
He also comes over when we dive in the area..Very strange thing is that amongst the Army Boat Squad members, he would ignore some members and hang around with others on a day by day basis ? The Lynx factor?
Remember before you jump in with your drysuit on to " Swim with Dolphins" that while cute and beautiful that they are wild animals and are quite capable of killing or seriously injuring you.
The trick if you meet a dolphin is to drive in straight lines / steady course which makes it safe for you and the dolphins. He will generally formate on your boat for 5 or 10 mins alternating between riding your bow wave and travelling beside or behind the boat before he gets bored and heads off again.
Be careful before you engage gear from neutral that he is not near the prop....in other words treat him like a diver.
Linking with the Azore thread and whales, one of the best experiences of Trans Atlantic was the visit each sundown of between 100 and 200 common ( Black and White) dolphins who you could see approaching at high speed from a mile or more away. They would formate on the boat and stay with us hopping and skipping for 15 minutes before heading off in search of another lone boat on the ocean.