Exciting Sighting en route to Guam

What do we do at sea? We went out on Deck 5, where there is a promenade on each side of the ship but not a circular route. We went forward to look at the big splashes the ship made as it went across good sized swells. As we were looking at the sea and spray, we both saw something coming toward the ship. It was dark, slender, and rising above the water about 3 feet. It might have been a periscope. No, that made no sense. It continued to come straight toward the ship and then turned sideways. As it turned sideways, we had a better view of what turned out to be the dorsal fin of a sailfish. Swimming parallel about 50 feet apart, the fish and the Tahitian Princess continued on their separate routes. It is so exciting for us to encounter any marine life and a sighting as unusual as a sailfish was a very special event.