Skipper's eldest son, Jacob, died more than thirty years before the gathering that is the event of the play Jacob's Wake. Jacob died because Skipper order him out to go seal hunting as a storm was breaking. Jacob was killed in the storm. The seal hunt and the return of the seals means the reminder of his harsh and unkind parenting, the loss of his son through death, his failure in life. As Skipper lays dying, his gohst appears to take command of ship to guide it through the new storm that is raging.
In Cook's Jacob's Wake, Skipper is an old sailor who has not only lost his legs while at sea, but more importantly his favorite son, Jacob. We can assume from the play's title that Skipper has, since that time, been mourning Jacob's death thirty years before, and the family (we witness) has been deteriorating even longer.
For Skipper, fishing was a necessity: the sea called the men to fish to be fed; but it has been the pursuit of seals ("swiles") that Skipper has been obsessed with—reveled in—killing them and taking their pelts, off the East Coast of Newfoundland. However, that obsession has cost him dearly.
Jacob was lost on such a journey, during a deadly winter storm at sea—much like the one building outside of the house throughout the play. It would seem that things changed in many ways when Jacob died. Skipper was injured on that trip and has been bed-ridden since that day—in a way, a large part of him died—and not just because he lost his legs. He loved the sea, but more so his son: and he relives that day repeatedly, perhaps sensing how poorly he looked after his family. However, in Skipper's mind, the family members have not only missed the magnificent experience of going to sea, but are also lesser human beings for staying on land: showing us that his obsession remains.
There were seals the day Jacob was lost. Skipper had pushed all the men to chase down the seals, even in the dangerous weather.
Git after them, damn ye. East...To the East. To hell wi' the starm. Ye can face into it. They must be East.
Skipper was so fixated on capturing the seals that he confronted the storm—personifying it:
Do yer worst, ye howling back devil. I'm not afraid o' ye, nor me boys neither...I'll git the men. Aye and the swiles too.
Battling nature has its price and Skipper pays with the loss of his son and his legs. He never goes to sea again, but as he relives that day in his mind, he is constantly on the alert for the return of the seals.
As the storm builds, Skipper goes over that terrible day: he has Rosie read his journal aloud, and he talks to Winston about it. He says the seals are in their element with the violent storms. And he draws comparisons between humans and seals:
...the young, helpless, floundering [seals]. But we be the same, boy, plunging and stumbling on the floes.
In a sense, Skipper alludes to man and seal being at an equal disadvantage: the young seals are helpless, but the men on the ice ("floes") are similarly so—and generally in life, it would seem. Skipper he looks forward to the return of the seals. He may speak of this literally (he says he'll crawl if he must to get to them) or figuratively, perhaps inferring to his death, maybe seeing heaven as a place where he can sail and hunt seals as he did years before:
The swiles'll come back in their t'ousands and when they do, I'll go greet 'em just like in the old days...
Skipper knows he is dying, and at the end, he is certain the seals have returned:
Did ye hear it that time? [...] No, b'y. A swile. They's a swile out there.
Just before he passes, Skipper says that the family ("house") is "adrift," comparing it to a ship lost at sea...
'Tis the shape of death, boy. I kin see'n jest like that first time...
He is referring again to that fateful day years before, but now infers that the entire family will be destroyed. The return of the seals also signals the destruction of the rest of the family—they will be taken as Jacob was taken.