I use a Benbo Trekker tripod on which the head can be attached to the bottom of the centre pole. The camera can therefore be supported at ground level, or below it if your subjects in a hole. The only downside is that your camera will be upside down which makes operation awkward. It has the bonus of having waterproof struts so can be used in several feet of water as well, but this is not recommended if your camera is in the position described above.