Extremely low level mapping

Here's a challenge :  I need to make a very low level "map" at about 3 or 4 Meters altitude (yep three !)   which can be studied in detail back at the university; with enough detail  to laboriously  identify, count and locate molluscs (muscles, clams and sea snails etc).  The reason this cannot be done in person is that it is a large area that is only rarely and briefly revealed on extremely low tides.  Am I on an impossible task here? ......  or can it be done ?