Do you experience panic in open water?

Here's something to keep in mind:  You only use the top 3' when you're swimming!  Everything below that doesn't matter! 

Many triathletes suffer from the murkiness and lack of a black line to follow.  Add to that the waves, sun, other swimmers, seaweed...

Do you have access to open water and organized open water swims?  Please don't do a lot of solo open water swimming, particularly if you are prone to panic. 

If so, you can improve things with familiarity, but to do so, you have to work out the mental stuff along the way. 

If you're driving to the swim area thinking:  "This is gonna SUCK..." or "Gosh, I hope I don't panic..."  the practice is likely to reinforce exactly what you're thinking. 

Instead, channel your inner river otter or sea turtle.  The swim is a chance to play and have fun.  Swim in some chest-deep water where you *can* see the bottom and stand up.  Swim underwater some, exploring the sand/mud/gravel on the bottom.  Float on your back.  Float on your stomach.  Don't be afraid to get some pool toys and dive for them, starting in somewhat shallow water and progressing to deeper and deeper water.  There may be a thermocline about 6-8' down, where the water temperature changes noticeably.  Explore it.  Granted, during a race you shouldn't be that deep, but...this is about acclimation.  Practice turning over and learning your inner ear helping you determine "up." 

I was a HS lifeguard and swimming instructor.  I'd have 5-year-olds concerned about touching the bottom in the deep end.  I'd tell them yes, you *can* touch the bottom, you just can't breathe while you're doing it!  I'd make a game out of getting down there, usually at the side of the pool where they'd let themselves sink down while keeping one hand on the wall.  We'd start in the 5' area, where they could keep a hand on top of the wall and still touch bottom, and then progress to the 8' depth where they couldn't.