Weather forced authorities in St. Mary’s County to conclude their search Sunday for a missing swimmer at Myrtle Point Park, but they plan to resume Monday as conditions improve.

Manuel DeJesus Portillo, 20, of Alexandria, Va., was last seen around 11 a.m. Saturday in waist-deep water in the Patuxent River, officials said.

A large group of his family members were spending the morning at the park, which has beach access to the river, when they lost sight of DeJesus Portillo, the St. Mary’s County Sheriff’s Office said.

Cpl. Julie Yingling said the young man’s family was spread out across the beach — some were fishing and others cooking — when they realized DeJesus Portillo had gone missing. They searched the area for close to an hour before calling 911, she said.

It is unclear whether DeJesus Portillo knew how to swim, but he had told his sister that he wanted to go into the water, Yingling said.

Authorities searched the river by boat and dispatched search teams around the park on all-terrain vehicles and by foot. They used drones to survey the peninsula, which is not far from Solomon’s Island, but heavy rain and choppy waters hampered efforts. Many parts of the region are under flood advisories.

Manuel DeJesus Portillo, 20, went missing early Saturday while spending the day at Myrtle Point Park in St. Mary's County, Md., He was last seen in waist-deep water in the Patuxent River by his family. (St. Mary's Sheriff's Office/St. Mary's Sheriff's Office)

Poor weather also hampered the search Sunday, but Yingling said the Maryland Department of Natural Resources expects to launch another boat late Sunday to look for any signs of DeJesus Portillo.

The man was last seen wearing a navy blue Hawaiian style shirt and black pants with a white stripe down the side.