I believe, In the abyss = inactive. Out of the abyss = active.
Exactly. The comparison is not between sea and abyss but instead abyss and death-stroke.
When the beast receives the death-stroke is when it 'is not', when it gets healed is when it 'ascends out of the abyss'.
In both cases it should be noted that it is AFTER the coming out of the abyss/death-stroke being healed that that is the time people are said to worship/admire the beast and that none of those who do so are written in the book of life.
[ 8 The wild beast that you saw was, but is not, and yet is about to ascend out of the abyss, and it is to go off into destruction. And when they see how the wild beast was, but is not, and yet will be present, those who dwell on the earth will wonder admiringly, but their names have not been written upon the scroll of life from the founding of the world.]
[3 And I saw one of its heads as though slaughtered to death, but its death-stroke got healed, and all the earth followed the wild beast with admiration. 8 And all those who dwell on the earth will worship it; the name of not one of them stands written in the scroll of life of the Lamb who was slaughtered, from the founding of the world.]
It is AFTER the death-stroke is healed/ascends from the abyss that the beast is given its 42-month authority. That is the time of GT, the hour of test/judgment to refuse to support/worship/take the mark of the beast.
[ 5 It was given a mouth speaking great things and blasphemies, and it was given authority to act for 42 months. 7 It was permitted to wage war with the holy ones and conquer them, and it was given authority over every tribe and people and tongue and nation. 10 If anyone is meant for captivity, he will go into captivity. If anyone will kill with the sword, he must be killed with the sword. This is where it calls for endurance and faith on the part of the holy ones.]
[ 24 And they will fall by the edge of the sword and be led captive into all the nations; and Jerusalem will be trampled on by the nations until the appointed times of the nations are fulfilled.]
[ 2 But as for the courtyard that is outside the temple sanctuary, leave it out and do not measure it, because it has been given to the nations, and they will trample the holy city underfoot for 42 months.]