One of the best places in Europe to observe whales and dolphins, like Sperm Whale, Short-finned Pilot Whale, Bryde's Whale and many species of dolphin. Most agencies depart from the harbour of Tazacorte on the western side of the island. These trips take you along the shore and a bit further off the coast and is great to see typical shore- and seabird species along the way.
Most common are the large flocks of Cory's Shearwater that can be seen mostly in the vicinity of whale and dolphin pods. Bulwer's Petrel tend to hang around in small numbers. Other species that can be seen, depending on the season of course, are Great Shearwater, Manx Shearwater, Barolo Shearwater and sometimes Balearic Shearwater, but you need a bit of luck for that one. Skuas might be possible too.
Terns can also be seen, but mainly close to shore, like Sandwich Tern and Common Tern. Also large flocks of gull hang around in the harbour from where you'll depart, like Yellow-legged Gull and Lesser Black-backed Gull.
You can observe most of these species from a vantage point from land, but you'll need a telescope for that. These whale watching trips are great to see these species up close. Many agencies depart from the harbour and you'll have a great array of possibile agencies to choose from.