In the Magnus quest Captivating Cruise, one of the instructions says I can dive underwater to avoid the ships. However, it doesn't actually seem to work, and I'm spotted by ships every time. On the other hand, I seem to be able to crouch in plain sight of the ships and they won't see me.

Suggestion: This isn't a particularly well done stealth segment, and most games that try something like this tend to fail pretty miserably... and I don't think this is an exception. Swimming stealth obviously needs to be fixed, and in addition, I think the frequency of the pirate ships needs to be halved so the player can have more time to navigate the clunky, awkward spaces of the broken ship. It's very easy to get stuck somewhere or have constant camera collision problems. Or really, the pirate ships could be removed entirely and I think it'd be more enjoyable as a simple story+scavenger hunt segment, kind of like rescuing Lara from the island. The stealth gameplay arguably adds very little to this particular segment.

Second feedback:

The player's "Effect Opacity" setting greatly affects the quality of these quests. Many vital graphics effects are almost invisible unless Effect Opacity set very high. Normally, I have this set very low, because otherwise this game's combat becomes a mess of excessive special effects, and I can't see what I'm doing. However, with Effect Opacity set low, I couldn't see things like the fire in Jordine's segment, the glowing interaction markers in this pirate stealth segment, and the pirates' red "vision" indicator was also near invisible.

Suggestion: effects that are VITAL to gameplay should not be tied to convenience options. Not everyone will notice or realize that these things are connected, and will end up being frustrated by invisible hazards.

Having same issue and additionally, the level design is very buggy , you can get stuck at them most random places, between some barrels while submurged and unable to swim or pull yourself out of water. Really terrible design of the place, so hard to navigate between search points and ofcourse being dead anytime you in the water because the DIVING to save yourself mechanic doesnt seem to work is making this a nightmare. 

PLEASE FIX THIS!

oh nice and when I completed it and went into the teleport, game crashed. Well done level designer!