Three crewmembers of the boxship Simba jumped over the side in the entrance channel at the port of Jacksonville, Florida on Wednesday, according to U.S. Customs and Border Protection.

The Simba departed Jaxport’s Blount Island container terminal at about 1230 hours GMT and headed outbound on the St. Johns River. As she passed near Naval Station Mayport, three crewmembers went over the side and made for the north side of the channel. They were spotted by bystanders, who contacted the police and reported the incident, according to local media.

All three made it to shore on Fort George Island, CBP told local Action News Jax, and one was apprehended and brought to the hospital for treatment. Two others remain at large, and teams from the local sheriff’s office and CBP are conducting a search.

It is exceedingly rare (and dangerous) for seafarers to try to leave their ship while under way. The circumstances of their decision are unclear, but agents hope to learn more by interviewing the crewmember who was hospitalized.

After the three crewmembers went over the side, Simba safely completed her transit of the channel and went to anchor off the port. She has since returned to a berth at Blount Island.

The Simba is a 2015-built container ship of about 6,900 TEU. She has been owned and commercially operated by the independent Singaporean line Sea Lead since last December, with shipmanagement provided by a second Singaporean firm. She has a clean port state control inspection record.