Beowulf’s preparations are shown in detail. An audience familiar with war and weapons would have been interested in this part. Did he wear his helmet, which would make swimming difficult? Yes, he did, and he wore his chain-mail shirt, too. Although swimming is much harder with heavy metal armor, it was important to Beowulf to wear some protective covering as he sank past the sea-monsters.
When he fought against Grendel, Beowulf had used no sword, being advised that Grendel was charmed against iron. In this instance, he accepts the ceremonial presentation of a sword from the shame-faced Unferth. Unferth’s probable high status at Hrothgar’s court is reinforced by his ownership of this weapon. If he was not a famous warrior himself, perhaps his father was; the sword is said to be an ancient treasure, never failing its owner. Now, armed with a sword, in chain-mail and helmet, Beowulf is ready to go.
Beowulf predicts that with the sword Hrunting, he will gain victory or die. Neither option will prove to be true, and one wonders if he would have bothered to take a sword with him, had not Unferth made a show of giving him this treasure-sword. Perhaps Beowulf wonders if Grendel’s mother will prove just as impervious to iron as her son; perhaps he is showing optimism so as not to shame an important man who has already suffered a downfall of pride. On the other hand, perhaps he would rather go into the water with a sword, just in case it works.
There are some surprises to be revealed in this fight with Grendel’s mother. The first is where Beowulf decides to go to find her: straight down. We might expect that she lives in a cave along the side of the mere, but Beowulf knows better, and he knows he must dive straight into the water.
Almost as soon as he has passed downward where the waiting men cannot see him, Grendel’s mother, who is indeed on the bottom, looks up and sees him. We have all seen underwater footage of sharks or men swimming at a higher, more sun-filled level than the cameraman; the water shines in the sun, and the body is clearly outlined. The mere must be murkier than the ocean water we see on film, but still it is through the sunlit background that the mother is able to see the intruder long before he sees her.
In the end, it saves Beowulf time, for rather than searching the mere’s bottom looking for a hidden lair, he is dragged very rapidly into it, perhaps before his breath has run out. Beowulf’s high-speed trip downward is fearfully dangerous; sea-monsters are clawing at him, tearing at him with tusks. Only his mail-shirt keeps him bruised but unwounded.
The next surprise comes at the bottom of the mere. We expect Beowulf to drown, as he would if a shark dragged him under the ocean waves. Instead, he finds himself in an air-filled underwater cave. Not only is it an underwater cave, it is more than that: it is a hall. The hall is not only air-filled, it is a real hall with a central fire. On the walls hang treasure-weapons, as perhaps there were at the hall of Heorot. The tables have turned: Beowulf the avenger is come into the enemy’s hall, as Grendel’s mother came to Heorot.