This is an interesting assignment, and it is full of possibilities for writing. The first thing you must do, of course, is think of yourself as a turtle; everything you write should be from a first-person perspective. Even more importantly, it should be from the perspective of someone who is very, very close to the ground and in water. If you look up, the trees near the pond must certainly seem like they can touch the sky; if you look out, the animals near the pond must seem like giants, as well. Keep that in mind as you write.
One possibility is to take a little journey and describe what you see along the way. This is your chance to look into a duck's nest, slide in the mud, or meet a new friend. Perhaps you can take an underwater journey in which you see all kinds of things, such as fish, snails, and moss.
Another option is to take advantage of being a water creature and describe all the tricks you can do while you're in the water (though of course you will do them slowly, since you are a turtle).
One more choice is to do something human in "turtle terms," such as go to school, babysit some younger turtles, play on the playground with your pond friends, or teach another turtle how to swim.
This is an opportunity to be creative, so you can do virtually anything you want. Enjoy!