Herring

Small vanilla friendly sub and well balanced for campaign. Elevator serves as an airlock. Just check it yourself and you won't regret. SOME PEOPLE EXPERIENCE INVISIBLE WALL BUG IN ELEVATOR. IN THIS CASE USE THE NO ELEVATOR VERSION (It is included in this mod)

"Herring" is an excellent (low tier) scout sub at a decent price. However, due to the budget cuts, fuel and energy efficiency leaves MUCH to be desired. (There is a reason why "recommended crew experience" is "experienced" level). Great if you want the sub which offers some challenge but is also rewarding.

Some tips !!! (I suggest reading)

Use 2 fuel rods instead of one and get the reactor and batteries upgrades ASAP. The sub is pretty cheap to balance your upcoming expenses (You can also immediately buy more expensive "A-class" tier 2 variant which is a way better).

Always charge the backup power supply when the ship is standby and use this power when accelerating the ship or doing power hungry maneuvers. Using the backup power supply right is crucial !

The battery in the command room is connected to the sonar, if your sonar goes black just flick it to passive for a few seconds.

Oxygen generator may not be working when rushing at full speed without the backup power supply turned on.

There are 4 safes on the ship. You can open them if you have matching tier keycard. Keycard tiers from best to worst: Blue (captain), Yellow (security, medic), Green (mechanic, engineer). Additional keycards are in the captain's locker.

The "A-class" version has better reactor, less power hungry devices and bigger weapon angles but also cost more. Easier to use. Your first option if you struggle with power management.

The "S-class" version is even better than the "A-class" and the discharge coil is replaced by unmanned drone.

The "(no elev)" variants have normal airlock instead of the elevator.