Antediluvian Abyss replaced Subsea as an official track since version 0.9.3. Subsea is still an addon, but it is way longer, and its graphics are not so advanced.
The track is most suitable for heavy karts. The lap takes about 40 seconds, so default number of laps is 3.
The starting grid is placed on a straight which ends with 3 items. The distance to the first corner is not so small, so the start has medium importance.
After a left turn, a player needs to complete a series of turns with increasing altitude. One can use the left side of road to collect small nitros, but the driveline after these turns is not so convenient in this case. This is probably the most difficult part of the track, as one needs also not to fall from the track. It ends with items with a banana, one should be careful with switches and driveline here.
Then, a long smooth right turn follows, which later becomes a long straight. It contains (again!) items with a banana, and in the middle of the straight there is a big nitro surrounded by bananas, which adds some difficulty to the track. The straight ends (again) with items and a banana.
Then a player needs to complete another long smooth right turn which becomes a bit sharp at the end, followed by a straight which contains items. This straight smoothly transforms into start-finish straight through a big long 180° left turn, containing small nitros on the right side and ending with alternating items and bananas.
The offroad is rather slow but you can still ride there if it is really necessary.
In general, Antediluvian Abyss is not the most interesting track to race online, thus being one of the least popular official tracks. Though, efforts should be put to achieve a perfect lap.