Three seconds.
That was the average window of time afforded to me to get any shots of river otters that decided to break the water's surface. Not the sharpest and greatest photos, but you can see this particular river otter enjoying the crunch of an Everglades crayfish.
It helps that otters are social, so they tend to move together in what a group is called a "raft". Tracking the wakes can help but following the small line of air bubbles was what helped me anticipate where the otter would break surface next.
They're quick snackers, so they'll only surface to chomp down on a nice crunchy crayfish for a few seconds before diving back down for more.