How long can I hold my breath before drowning in Another World?

In Chapter 5 (City 2) of Another World, there’s a section where you need to swim underwater to shoot and disable a power line.

When I try swimming down in one go, I end up running out of breath. I need to make sure to come up for air half-way through. A few close calls have made me curious how long I can stay under.

How long can I hold my breath underwater before drowning?

40 seconds, sink or swim.

If you drop like a rock, it is 40 seconds.
If you swim the whole time, it is still 40 seconds.

You must take a breath of air in the middle of this area. (From the splash, it would take ~45 seconds to complete the run.)

Take the path DOWN-2, LEFT-2. There is a room with four branches here:

• Choose the tunnel in the upper-left to reach the air pocket. With no wrong turns, this takes ~30 seconds from the start.
• Choose the tunnel in the upper-right to reach a dead-end. This will require an additional ~10 seconds.
• From the air pocket, take the path DOWN-1, LEFT-1. There is a pile of rocks, and you will have to swim against the current going back. This entire round trip requires a total of ~40 seconds.
• From the air pocket, you can make it to the end in ~15 seconds.

In an otherwise very difficult game, this is not a very tricky area to maneuver. There are only four branches, and the creatures on the floor can't even hurt you while you are in the water.