Although not marked on the chart, there are heavy overfalls in the passages to the south and north of LeMesurier Island. These posed no significant problems in winds of 10-15 knots but local fishermen say this area can be treacherous in stronger wind over tide situations and there have been occasions when even the large Alaska Marine Highway ferries have been unable to transit the passages. The South Passage is said to be the calmer of the 2.