The distance and the possibility of high waves will prevent small boats from conducting animal studies.

A chain was strung through the water from the base of the tower to prevent boats from traveling into the river port.

But the bridge then remained in the down position for days, preventing boats, including some laden with heating oil, from reaching their destinations.

And the Cole does not appear to have created an exclusion zone to prevent small boats from approaching.

The bridge has very little clearance below it, and this prevents boats from passing under it.

It is lowered in the winter, when ice prevents boats, so that snowmobile traffic can enter under the roadway.

The pounding surf prevented boats from being launched from the ship or the shore, and a number of the crew were swept away.

The drawbridge section is closed for a certain period of time to allow trains to pass, which prevents large boats from passing under.

This lowered the tide head to Old Ford, and prevented large boats sailing the river until the 15th century.

It was built by in the 16th century to prevent Turkish boats from reaching the port.