This answer is taken from a previous discussion on this topic, which can be found here.

The Royal Navy's Landing Craft Assault (LCA) was designed to carry an infantry platoon of 31 men. This was the strength of a platoon in the British Army when the LCA was designed. However, as war experience was gained, the number of men in the platoon rose to 37. This, combined with the need to carry specialists like engineers, meant that platoons typically landed understrength.

The platoon was composed of three eight-man sections, plus a four-man command section and a three-man mortar section. From 1943, each section was composed of ten men. A standard loading was devised for the LCA, to ease boarding and reduce confusion. This chart shows the loading pattern. The three rifle sections sat on three benches running down the length of the craft, with one on the port side, one on the starboard side, and one in the centre. One section's Bren gunners (armed with the Bren light machine gun) was in the port cockpit, to provide covering fire on the approach to the beaches. Sometimes, the other two section's Bren gunners would also be involved, with one entering the starboard cockpit to fire on the beaches, and the third staying in the centre to provide anti-aircraft fire. The platoon commander stood at the front of the craft. The LCA had a set of armoured doors behind the ramp, to protect the troops on the approach to the beach. When the LCA hit the beach, he would open the armoured doors while the naval crew lowered the ramp. He would then lead the platoon out onto the beach, followed by his batman (officer's servant/assistant) and runner. The section on the central bench, typically No. 1 section, would then disembark, then No. 2 and 3 sections from the side benches. Finally, the platoon sergeant (the second-in-command) and the mortar team would land.

There were often exceptions to this. The 1942 standard loading arrangement called for the LCA to carry a five-man engineer team, with five men from the platoon being left out. This engineering team would be seated in the front rows of the craft, behind the platoon commander. This would let them get out and onto the beach to deal with obstacles as soon as possible. At other times, mixed units would be loaded onto LCAs, with men from different platoons or specialists from the company level being added to the load. Even on these, it was typical for a platoon commander or their equivalent to lead the men out onto the beach.