You look thoroughly at your direct representative and tell him, as usually by telepathic means, that no dolphins shall be harmed. You exclaim that they are wonderful creatures and of great joy to you. The manateeman nods and faces the village. He jips and japs what you just told him and the manateepeople are listening. They begin dancing and singing afterwards. This seems to be their way of showing you that they'll comply to your demands. Maybe if you send them to practice they will actually sound good. Hmm.
Afterwards you decide to amuse the manateemen, by giving them some sort of gift from the ocean. So you go back into the sea, trying to look for the deep blue. After a while of swimming, you ate some delicious hammerhead on the way, you find a deep shaft going deep into the ocean. As you swim downwards you notice it is actually getting warmer, which is only pleasant to your being, as your diet has made you thermophile.
And there you see it. Beneath you a humoungous lavastream. You feed on the hot liquid rock and feel delighted. After exploring the aquatic cave you find a round rock of obsidian, which has a diameter of aproxiamately 7ft. You decide that this is a peculiar object, and also it would be nice to introduce the concepts of rocks to these backward manateepeople.
You carry the rock to the village and present it to them.They sing and dance.