Fun Facts About the North American River Otter: They can swim up to 12 mph and can run 18 mph. Otters swimming beneath ice for long periods of time are known to use trapped air bubbles to continue to get oxygen. River otters close their nostrils and ears while underwater, and can hold their breath for about 4 minutes. The maximum known time for an otter to hold its breath is 8 minutes. Otters view their environment with a variety of senses, but their whiskers are very sensitive to physical sensations, and are important in hunting.