My friends and I were in South Padre Island for a friend's wedding. We wanted to go on a dolphin tour and of all the tours available on the Island, Isla Tours came highly recommended.
We went on a 1.5 hour tour of the Gulf of Mexico. At first we were trolling for underwater sea creatures, but all we were able to get were a couple of starfish and a jellyfish. We were able to hold the starfish while the first mate explained about them. We didn't hold the jellyfish as we didn't want to get stung, but we were able to pet it, so to speak.
Once they were returned to the gulf, our boat sped up in the opposite direction so that we could watch for dolphins, and they did not disappoint us. The boat slowed down so that we could take pictures or record their activities for posterity. Once we sped up again, the dolphins decided to swim along our boat.
Although there was a family of 140+ dolphins where we were located in the gulf, we only saw a few of them, but enough to make our experience worthwhile.
An affordable, educational experience I would highly recommend if on SPI.