When wrecks are in deep water, divers are physiologically limited to the amount of time they can spend at depth. Fortunately, the wrecks in this project are in shallow water, so that's not a big problem here. Water temperature, too, can cut down on the time researchers can spend researching. We're lucky on that score, too. Air temperature is very important as well.
Cold weather makes the time between dives uncomfortable and drains the crew of energy.