Hmmm. Interesting question. Lots of possibilities, so I'll just go with my first instincts.
The star around which I revolve is somewhat cooler and smaller than Sol. We might as well call it Tau Ceti for now. I orbit the star at a closer distance than Earth does Sol, resulting in a shorter "year" but roughly the same kind of climate (the "habitable zone.") I am tilted at the axis less than Earth, resulting in less extreme seasons. I rotate more slowly than Earth, resulting in long "days." There is a single, smaller, rocky and airless planet nearer to my star than I am, and a few larger planets farther from it. (These are not quite large enough to be gas giants, but have atmospheres of various compsitions, several moons each, and complex ring systems.) There is no asteroid belt. I have no moon.
My surface consists mostly of water. There are no large continents, but there are countless islands of various sizes everywhere. (For now, let's call me "Archipelago.") There are two small ice caps. My climate, on average, is a bit cooler than Earth, but also less extreme.
Life on Archipelago is, of course, extremely complex. Let's assume for now that there are analogues of bacteria, viri, and so on. On a macroscopic level, you would first notice that the single world-girdling ocean (a bit less salty than Earth's, and, of course, without tides) teems with fish analogues. Of course, the smaller the creature, the more of them there are. The largest is about the size of a dolphin. Of course, there are plant analogues everywhere as well, much of which resembles floating seaweed. The surface of the ocean would often seem to be a blue-green patchwork constantly in motion.
The equivalents of plants, insects, and amphibians also inhabit the land areas. None of the animal life is yet completely free of the water. There is nothing as large as the tree, but there is a large variety of bush-sized organisms.
The "inhabitants" of Archipelago are more massive than humans and lower to the ground, walking on four legs and making use of two arms. Each hand has two "thumbs" and three digits between them. To human eyes, they would look something like large gray lizard people. Their civilization is on a Stone Age level, with simple spears used to catch fish. They also eat lots of leaves. Much of their time is spent in the water, although they are air breathers.