Inner Range or the Culebra/Vieques Complex as it would be known until 1975 and the closing of the Culebra subranges. The amphibious exercises were transferred from Culebra's Flamenco Beach to Vieques, and naval gunfire practice began on Flamenco Beach and on the adjacent Flamenco Point. The 1st Brigade had revealed many of the same mistakes seen in FLEX1 but encountered several new problems. The Marines needed to get closer to the beach and the battleships were not able to tread in shallow waters. As for the landing craft boats, the problem was still not resolved as they were slow and extremely vulnerable. In several testing of various boats, they found that they proved to highly unstable for gun platforms, dangerous in disembarking the troops and were incapable in crossing submerged coral reefs. The uses of smoke and darkness to conceal the beach landings were still causing confusion amongst the landing parties. While the artificial naval gunfire tests were being continued, the rapid area fire had made the aerial spotting difficult for the pilots. And still communications were a problems. However, the barrage-type bombardment met the approval for the Army Officer-Observers to reinforce a fundamentally sound doctrine. The Marine brigade gained tactical experience in the amphibious maneuvers ashore but the FLEX 2 had not made any significant breakthroughs in fixing the problems encountered during FLEX1. FLEX 3 The Fleet Landing Exercise Number 3 was conducted on San Clemente, California from January 26 to March 3, 1937, in agreement with U.S. Attack Force Operation Plans 1-37 and 2-37. The 1st Marine Brigade was transferred to San Diego for the exercise and was absorbed by the small-sized 2nd Marine Brigade; the whole Fleet Marine Force. Also present were the understrength provisional Army 1st Expeditionary Brigade. And once again, the testing problems of previous exercises presented themselves. The heavy California surf proved the landing boats were infeasible for beach landings; the Navy coxswains disembarked their troops too far from the beach, broached their boats, or dispersed the concentration of the landing in scouting out better, safer landing spots. After five standard-type naval boats foundered in four-foot surf, efforts to adapt these were ended. They were criticized for lacking speed and maneuverability and being difficult to handle in surf. The experience proved conclusively that a specially designed landing boat with superior power, maneuverability, protection and surf-riding qualities was vital for landing operations. Smoke and darkness