GULF OF GUINEA — Petty Officer 3rd Class Alex Seda Martinez, a machinery technician aboard the U.S. Coast Guard Cutter Thetis (WMEC-910), opens a valve to check compression on the main diesel engine Friday, April 19, 2019 prior to conducting power trials on the main diesel engines while underway in the Gulf of Guinea. U.S. Coast Guard photo by Petty Officer 2nd Class Jonathan Lally