The Royal Navy used three main ASW weapons during the course of the war. One was the classic depth charge, the other two were 'ahead-throwing' weapons, which launched charges over the bow of the ship.

Depth charges were the simplest weapon. They were, simply, a weighted container full of explosives, with a hydrostatic 'pistol' to detonate it at a pre-selected depth. They could be rolled over the stern of the ship, or shot over the side of the ship using throwers - essentially a very simple mortar. All ships with depth-charges would carry rails or chutes for rolling them over the stern, and most escorts combined these with throwers. In the RN, the charges were deployed in standard patterns, calculated to maximise their effect. It started the war using a five-charge pattern, dropping the charges in a cross pattern with each charge spaced 40ft (12m) apart. This proved to be ineffective against deep-diving U-boats, so a ten-charge pattern was introduced. This was simply a doubling of the five-charge pattern, with five more charges laid at a deeper depth in the same pattern. In December 1940, a 14-charge pattern was introduced. This added in four new charges, thrown at 45^o angles to the motion of the ship. However, experiments in November 1942 showed that some of the charges in this pattern were interfering with each other, reducing their effect, and causing some to fail. A depth charge damaged the hull of a submarine through its blast. Water, being incompressible, magnified the effect of the blast compared to a similarly sized explosion in air. Near-misses, while not deadly, had a significant morale effect on submarine crews, and could do strucutrual damage too.

The Royal Navy used, over the course of the war, three main depth charges. These were the Mark VII, the Mark VII 'heavy' and the Mark X, or 'One Ton' charge. The Mark VII, introduced in 1939, had a charge of 290 lbs of Amatol explosive. It was expected to have a lethal radius of ~30 feet, but in service, this turned out to be more like 20 ft. It sank at a speed of 7-10 ft/sec, making it a rather ineffective weapon in conjunction with the poor early Asdic (sonar) sets. The Mark VII 'heavy' was an upgraded version introduced in late 1940. It had an additional cast-iron weight to increase the sink rate and, from 1942, a charge made from Minol. The cast-iron weight increased sink rate to 16 ft/sec, while the Minol charge was lethal out to 26 ft. The Mark X could only be launched from a 21in torpedo tube, limiting the deployment to just destroyers, but it was far more effective. It had a sink rate of up to 21 ft/sec, depending on precise model, and a 2000 lb charge, from which it took its name.

While depth charges were a useful weapon, and could easily be fitted to most ships (though they weren't typically fit to merchant ships), they had their limits. They could only be deployed behind a ship, as otherwise their blast would do serious damage to the ship. However, Asdic/sonar could only be used towards the front of the ship, as otherwise the noise of the ship's engines and propeller would overwhelm the sonar signals. This meant that, as an escort passed over a submarine to drop its charges, it lost contact with the submarine. This, combined with the time the depth charges took to sink, gave the submarine a chance to make evasive manoeuvres and move out of the danger zone. To solve this problem, the RN developed ahead-throwing weapons. These could be fired forwards, allowing them to be fired at a target that the escort was in sonar contact with. There were various trials with these weapons in 1939-41, but the first that was adopted was Hedgehog, in 1942.

Hedgehog was a spigot mortar, a fairly rare type of firearm where the barrel sits inside the projectile, rather than the other way round. The projectile contains a tube with a propellant charge; this tube fits onto a rod or spigot on the mounting. The typical Hedgehog installation had 24 spigots, in six rows of four and fired 65 lb projectiles. The spigots were arrayed such that, when fired, the bombs would land in a 100 ft diameter circle (or ellipse, if the mount was tilted) about 200-300 yards ahead of the ship (depending on speed). The projectiles were fired in a ripple pattern, as firing all 24 rounds at once would do serious damage to the ship. Once the rounds hit the water, they sank at a speed of about 20ft/second. The bombs were contact-detonating, exploding only if they hit the hull of a U-boat. Their explosive charge, of 31-35lbs, was small enough that it was judged that they would not be effective with a hydrostatic fuse. However, it would blow a hole in a submarine's hull if it exploded in contact with it. Hedgehog was first fitted in February 1942, but most captains were wary about it; the lack of explosions made it feel ineffective, and there were, initially, frequent jams and failures, most notably one that seriously damaged the bridge of HMS Escapade. However, it eventually proved its worth, scoring its first kill in November 1942. It was more effective than depth charges, but was not as effective as first hoped.

From September 1943, another ahead-throwing weapon was introduced. This was Squid, a three-barrelled mortar. Each barrel fired a 390lb depth charge, containing 207lbs of explosive. The three charges would land at each point of a triangle with 120 ft sides, about 300 yards ahead of the ship. They sank at a rate of 44 ft/second, and had a hydrostatic pistol. The mounting could be tilted by 30^o, to cancel out the roll of the ship and to allow for adjustments of aim. The Loch class frigates had Double Squid; this was just two Squid mountings, separated by 60 ft. Each mounting could be fired together or independently. Squid's main advantage was that it was directly linked to the ship's Type 147 Asdic. This allowed the point of aim and depth setting for the charges to be continuously set up until they were fired. Squid was highly effective, with a nearly 50% success rate.

There were several other weapons, mostly used against surfaced subs. Ramming was commonly used, but discouraged as it risked serious damage to the ramming ship. Guns were useful, but a sub's thick, curved plating could be hard to penetrate. A specialised anti-submarine shell, Shark, was developed and issued. Mines were often laid off U-boat bases, and to defend British ports and bases. British submarines would lurk off U-boat bases, and sometimes engage them with torpedoes. Over the course of the war, the Germans would lose a total of 264 U-boats to ships, 250 to aircraft (plus another 43 bombed in port and 37 shared between aircraft and ships) and 35 to mines. Three more were captured, and 46 went missing, with no indications as to their fate. Overall, a total of 28,000 German submariners would be killed, from 40,900 enlisted. Another 5,000 would be captured by the Allies.