We took the whale watching trip from Playa Santiago and we weren't disappointed. We saw lots of dolphins and a family of pilot whales. The trip includes swimming off the boat at a secluded beach and lunch of grilled tuna, canary potatoes with mojo and a selection of salad. Plenty of drinks are provided with lunch and there's a toilet on board.
There was quite a swell during our trip and several people were seasick, so I would suggest taking precautions beforehand if you suffer from motion sickness like I do. I used the acupuncture wrist bands and I was absolutely fine.
We really enjoyed this trip because it allowed us to see the island from a different perspective. It was 45 euros each but worth it.