For above water shots, try shallow streams maybe... and just shoot from above enough to block out any foliage along the bank. If you want that vast ocean feel, you might wanna try creating an anchor with some fishing sinkers and attach them to the boats hull with waterproof tape... just make sure the line is long enough to reach the waters floor... also, playmobil makes a watertight mini engine you can attach with tape to your boats which give off a cool wake behind the boat.