You play as the UEO seaQuest DSV 4600. In normal gameplay, you get 20 points for destroying a fish or an enemy sub, 50 points for each diver you rescue, and 10 * your remaining oxygen when you rescue the divers. Using the No Despawn glitch, I collide with a fish for 22 minutes until I reach the maximum score of 999999. Credit goes to VELHO for discovering the glitch.

Normally, when you collide with a fish or enemy sub, the enemy despawns immediately, and seaQuest (your sub) despawns 35 frames later. However, by colliding with an enemy in a special way, you are able to prevent the enemy from despawning, which keeps the seaQuest's despawn timer from completing. In this case, you get 20 points for every frame you are in contact with the enemy.

Using this method, it takes 22 minutes and 53 seconds to reach the maximum score of 999999. At this point, the enemy swims away (without ever despawning), and the kill screen is shown. In the kill screen, the "Activision" text at the bottom is replaced with "Copyright 1983", though you never actually die. This is the same behavior as when you reach 999999 by means of normal gameplay.

For comparison, see this [dead link removed] savestate, where 999999 is reached by normal means. After a few seconds, the seaQuest will collide with a fish, "Copyright 1983" will be shown, and the seaQuest does not despawn.

To summarize, this max score TAS of Seaquest is different from Virtual Pinball because there is a clear ending point here. It is also different from Tetris because you don't need to die to win.

In order for the glitch to work, the seaQuest's X position must be 8 greater than the fish's X position. Because the fish does not even appear on the screen until frame 278, the TAS contains playaround gameplay until the fish is ready. The seaQuest's maximum X position is 134, and the fish in question enters from the right (higher X) side of the screen, so the earliest we can trigger the glitch is when the fish's X = 126.

For this first fish, you must collide with the right (back) side of it to trigger the glitch. This collision would normally involve the hull of the seaQuest, but if you clip the top right corner of the fish's collision mask, you can collide using the seaQuest's rudder so that you are still facing right. This saves 1 frame.

Here, have a RAM watch file.

Noxxa: Judging.

morningpee: Remaking with a different goal. See this post