When my kids were younger, we scheduled a swim with dolphin tour. We were all geared up in our scuba suits and waiting on the pier for the boat from the previous tour to return to take us out. When the boat rushed back in, they were carrying this guy just covered in blood and holding big patches of skin on him by hand. They cancelled our tour... only explaining that the dolphins weren't in a good mood that day, ha ha. We went back to our room and looked it up, and many of these tours end up in chaos, because dolphins are wild unpredictable animals. We don't know what sets them off, but they have rows of razor sharp teeth that can F-you up in a heartbeat.
The tour guides will always blame the customers, but the reality is that it could be anything from what shampoo someone in the tour used to an arm gesture one would make that sets them off. They have no idea what it is... but these places still continue to take tourists' money.
Now, if I am swimming out beyond the breakers, which I wouldn't do on purpose, and if I see dolphins, I hurry my ass back towards the beach. F them dolphins. Ha ha.