Just before the July 4th weekend, one of the busiest boating times of the year, officers are going out in full force on Minnesota lakes and rivers to crack down on drunken boating.

It's part of the annual enforcement campaign "Operation Dry Water," a national effort to deter drinking while boating. Authorities are ramping up patrols Friday through Sunday, just before the holiday.

The extra efforts were announced Friday by the state Department of Natural Resources and local law enforcement, who took their message to Lake Minnetonka, where the most boating while intoxicated (BWI) arrests are made in Minnesota every year.

"Drunk boating is drunk driving … you're just in a different device," said Lt. Adam Block of the DNR.

Officers on the 14,000-acre lake, the Twin Cities' largest and most popular, were inundated with emergency calls last July 4th weekend, especially alcohol-related medical calls. Deputies reported a rise in underage drinking and serious calls — including unconscious intoxicated boaters, a man who suffered a spinal cord injury after diving into the shallow Cruiser's Cove and a woman whose leg was cut by the propeller of a boat backing into her.

This year, authorities are boosting enforcement, having four to six boats on Minnetonka at a time this weekend and 11 on July 4th weekend. They'll be citing drunk boating and underage drinking, which is also on the rise. Lt. Kent Vnuk with the Hennepin County Sheriff's Office Water Patrol said deputies have issued 34 underage drinking citations over two weekends this year; typically they issue 15 a year.

The blood alcohol limit for operating a boat, just like land vehicles, is .08, and violating that can result in fines, jail time or loss of boating privileges.

Statewide, BWI citations have stayed relatively flat recently, with 80 BWIs in 2015 compared to 76 in 2014 and 89 in 2013, according to the DNR. But on average, more than one-third of boating fatalities involve alcohol; in 2015, alcohol was a factor in seven of 16 deadly boating accidents.

Kelly Smith • 612-673-4141