Some ideas for creature interactions with Cyclops

Tenouchi

Shallow depths - Objective: add some immersion to the Cyclops experience and at most provide a minor nuisance that encourages the diver to exit and interact a bit.
*The balloon creatures that attach to and lift rocks could attach themselves to Cyclops if it moves through an area they grow in. Enough balloons on your Cyclops could make it harder or impossible to descend. Removable by exiting to pick them off by hand, or by descending below say 150m where they will release on their own due to pressure.
*If Reefbacks end up with an ecosystem of creatures that follow them around, it would be fun to have these creatures also follow the Cyclops if they happen to meet. Reef fish would love to hang out in the shadow of a sub.
*Get plant matter stuck in engines if you spend a lot of time plowing through sea vines. Can be removed by hand.

Mid depths – Objective: introduce concepts important for survival later in deep depths, still more interaction with environment.
*Add toggle options to Cyclops for lights and engines.
*Introduce a creature that is valuable to the player (it makes a large amount of food or drops a valuable substance), but will flee if it hears the Cyclops engine or other loud noises (banging into things) too close. Player spots these from Cyclops and learns to cut the engine before exiting to pursue.
*Small luminescent schooling creatures will be attracted to the lights of the Cyclops when stationary. These could potentially attract predators. Not a big deal for the Cyclops but the player can cut the lights to avoid coming back to find sharks hunting the area.

Deep depths – Objective: creatures that reasonably threaten the Cyclops, while remaining dependent on player actions.
*Add sonar ping module. Audible pings indicate nearest large objects distance from the sub. Something far: ping…………ping………..ping. Something closing in: ping….ping…ping.pingpingpingpingping (whatever it is, it’s right under us!)
*Add sonar map module. Shows these objects on a 3d sphere around the sub. Larger blips are larger things. Shows player where to retreat.
*Add electric hull module. Uses large power to zap anything in immediate vicinity. Stuns most creatures, scares away big ones.
*Creature that hunts the Cyclops:

-Should be about as big or larger than the Cyclops itself
-Solitary hunter
-Deep sea creature, so relies on sound and the Cyclops own lights for tracking
-Territorial
Typical encounter: Alerted by the engine sound of Cyclops approaching, swims to mid range to investigate, if lights are on or engine continues running, will approach the sub closely, decides to attack sub or not based on an aggro meter that fills up during the time it spends near the sub. Lights and sound increase the meter, silence and darkness lower the meter. If meter bottoms out, swims away. If meter crosses threshold, decides to attack. The attack is very noisy and rocks the ship around, causing leaks that need to be managed. If engine and lights stay on, the attacks will increase in frequency until player can’t keep up with the damage. If sub stays quiet, the creature may poke a few more times and circle the sub looking for a response, before eventually swimming away.
-Using the electric hull while under attack would cause the creature to retreat some distance, and give 20 seconds or so before resuming the attack behavior.
-Creature maintains the aggro meter for each vehicle separately. So a Sea Moth/Exosuit/Player fleeing a doomed Cyclops with high aggro will not be chased. But a sea moth exiting a low aggro Cyclops will become the new item of interest for it. Player could potentially save a medium aggro Cyclops by exiting in Sea Moth and getting the creatures attention, then fleeing to a small cave or abandoning the sea moth (with brass balls) to swim back to the Cyclops.
Awesome encounter: Same as above, except the noise of the sub or the noise of the attack itself attracts another Cyclops predator. The predators are highly territorial and disengage the Cyclops to threaten and possibly fight one another while the player slips away.
Super awesome encounter: Same as above except the noise of the attack attracts something much bigger than both of you. As it approaches on sonar, the Cyclops’ predator flees only to be chased down by the much bigger threat, leaving the player in eerie silence and feeling very small and vulnerable in this normally big awesome sub.

*Creature that attacks the Cyclops to defend an area (nest?)

-1/3rd size of Cyclops
-Luminescent spots for attracting prey, being visible to player
-Found in groups protecting things the player probably wants to get ahold of
Typical encounter: Long distance, ignores player entirely. Medium distance, one creature breaks away and advances on Cyclops control window. At first just views the player with curiosity, but acts increasingly aggressive as Cyclops continues to approach defended area. Low distance, creatures attack. Bashing into the ship causing mostly minor damage while trying to push the ship away. Causing some leaking and lots of noise that can attract other things - turning this into a possibly super awesome encounter.
-Player can spoof these creatures into engaging the Cyclops while player raids their stash. Getting the Cyclops attacked plus deploying the electric hull would be very effective for raiding the loot. Could also lure other large creatures into their defense zone to do the same.

*Derpy fish attracted to lights

-Attracted by lights. Will mill around the ship and bump into it, causing noise - increasing chance for fun encounters.

Seldkam

Can't read all this but it sounds awesome what I did read... Check out the reaper leviathan