Issues with Hydra

[Revelanth]

Just now I had a quick dive with bots and was lucky to get the new biome.
General difficulty seems to be appropriate for a second layer biome and the visuals are gorgeous. Naturally, I've had limited experience with the new boss and its intricacies remain unknown. That being said, I've had great difficulty with the adds the Hydra produces as it sustains damage. They were quick and seemingly impervious to non-torpedo damage. I had to pilot the sub and due to the frantic nature of the fight had no time to man the weapons. If offspring's superb durability/invincibility is intended this makes the game potentially unplayable in singleplayer.
Also, after the sub was totaled and obituary published the cheevo for beating the boss popped. It was nowhere near to being defeated, its healthbar having been reduced to ~40%.