Sediments and coring conditions can be highly variable at any site, particulary in inland waters. A simple reconnaissance prior to the vibracoring survey is a very good investment of time.
Usually this involves going around to the prospective coring locations, and probing the bottom with a length of narrow steel pipe or conduit, provided the water is shallow enough. For deeper waters a heavy pipe or rod, tied at one end to a rope, can be dropped into the bottom, and its penetration guaged by the difficulty of pulling it out. Any degree of penetration indicates that vibracoring is likely to be successful. The object is simply to find out if coring is feasible at that spot, since a majority of the time in any coring survey is spent just anchoring the boat and preparing to core.
This is also an opportunity to note the water depth and any boat hazards, and to mark the site with a GPS coordinate, bouy or stake. A visual marker is a great help later in positioning and anchoring the coring boat directly over the spot. The recon also allows the field crews to plan shore access points where supplies can be picked up and cores handed off to a courier for quicker transport to the processing site.