The first vessels have passed through the Strait of Hormuz since Iran and the U.S. reached a two-week ceasefire deal, ship-tracking service MarineTraffic said Wednesday.

But more than 12 hours into the ceasefire, overall traffic through the vital waterway has not picked up beyond the slow trickle it has experienced throughout the war, experts and industry professionals say.

Uncertainty and confusion in the maritime industry remain high, despite Iran’s assurance that vessels will be able to safely navigate the strait during the ceasefire.

That confusion stems in part from Tehran’s caveat that passage through the strait is only possible “via coordination with Iran’s Armed Forces and with due consideration to technical limitations.”

The potential for Iran to heavily toll ships is a key sticking point, a marine insurance executive, who did not want to be named on the record, told CNBC.