If it is "in" the water, yes. Otherwise, it does not float but must somehow propel itself to rise in the water.
If it is "on" the water, no. At least, not necessarily. Because of surface tension, some things are able to float even though they are heavier than their equivalent volume of water. They do so by not breaking the water's surface tension. The molecular cohesion of water's surface can bear a weight slightly heavier than the water beneath it will buoy. You often see this with insects. They float on the water because they don't break the surface tension, but if something pushes them below the surface of the water, they sink.
A little science experiment you can do at home to prove some things heavier than water can float on water is with a small sewing needle. Sewing needles are heavier than their volume of water, meaning they have a specific gravity of greater than one. You can prove this by holding a needle vertically over a bowl of water and dropping it in. It will quickly sink to the bottom and stay there. It will show no buoyancy. That proves the needle is heavier than its equivalent volume of water. However, with a pair of tweezers, you can then gently place another identical needle, or even that same needle if you fish it out, onto the surface of the water by holding it parallel to the water's surface and then releasing it as close as you can get it to the water without touching the water. The needle will land on the surface of the water and float indefinitely. It will only sink if you break the surface tension of the water by jarring the bowl or if you push it below the surface. As soon as it sinks below the surface, it will sink to the bottom. That's not because it floats like a steel ship, which floats because of displacement and sinks when pushed below the surface and water fills up the places where water had previously been displaced from. Basically, the ship floats because so much of its total volume is air, air that remains air because the steel hull is displacing water that would otherwise replace it. Unlike a steel ship, however, a sewing needle is solid, so there is no displacement, no water rushing into places within its volume where water had not previously been when you push it below the surface. Rather, that needle floats because its weight being distributed over the needle's surface area that comes in contact with the water when it is placed horizontally isn't enough to break through the water's surface tension even though the needle itself weighs more than its equivalent volume of water.