The Navy sank a second ship during a live fire exercise at sea Tuesday night as the Rim of the Pacific international navy exercises continued in waters off Hawaii.

The decommissioned 44-year-old cargo ship USS Concord was used as target practice in waters 15,390 feet deep 61 miles northwest of Kauai at 4:12 p.m. Tuesday.

On Friday, Navy  and allied ships and aircraft sunk another decommissioned cargo vessel — the USS Niagara Falls — 63 miles northwest of Kauai.

One other decommissioned vessel, USS Kilauea, will be sunk as part of the target practice exercise during RIMPAC.

The Navy said the sink exercises provide “the opportunity to gain proficiency in tactics, targeting and live firing against surface targets, which enhances combat readiness of deployable units.”

The environmental groups Basel Action Network, Sierra Club, Earthjustice and Center for Biological Diversity have condemned the Navy’s ship-sinking exercise.

The Navy said it follows Environmental Protection Agency regulations and that the target practice takes place at least 57 miles from land and in waters at least 6,000 feet deep.

Surveys are conducted to ensure that humans and marine mammals are not in an area where they could be harmed during the event, the Navy said.