I just finished my first Sprint Tri a couple weeks ago and was super pumped! I bike and run regularly. I knew how to swim but never having swam laps in my life, started swimming about 2 and a half years ago for 3-4 months straight to get ready for a Sprint Tri that didn't happen until 2 weeks ago (Moving across half a country, a new baby, and a new job took up a bit of my time! ). I hadn't been in the pool since those 3-4 months, and I did about 5 pool swims and a couple open water swims (one with a wetsuit) to get ready for this one.

1) How are you when you swim that 10th of a mile? A comfortable steady front crawl? A pretty out of breath rest-on-the-wall every length front crawl? A completely out of breath at a 10th of a mile swimmer? You really need to realistically assess your swimming level so that you can start safely. Me? My first swim was in the shallow end and 200m in I was spluttering and laughing at myself while walking on the bottom thinking "is this seriously this hard?"

Took me a good 4-6 weeks to be comfortable doing 1km swims (swimming 2-3x/wk), took me right around 30min. No swim clubs and some youtube videos. Depending on your level, like btpdragon first suggested (and what I should have done in hindsight), join a Master's Swim Club, should be easy enough to Google for you. I could only imagine how beneficial that would have been.

2) After you're comfortable with the distance in the pool, you should 100% do some open water swimming. Though I hate to admit it, even starting to swim in the deep end was a bit of a head game for me (and I'm really not one that's prone to being anxious). The jump from pool swimming to open water swimming is an even bigger head game in my opinion. The dark water, not seeing a bottom of any kind, temp. changes, waves, sun in the eyes at times, no re-assuring pool edge in site...it can be intimidating, do it a few times before race day...maybe you won't have any of those anxieties, but it's better to know it doesn't bother you beforehand, and have the time to get over any issues that might come up prior to race day if you do.

3)Goggles. Not sure why, but even my goggles fogging could wreck my concentration. Kept trying "spit" but that didn't work at all for me. What DID work was Johnson's and Johnson's Baby Shampoo. I put a tiny dab on my finger and lightly coated the insides of the goggles, then rinsed them in the water...worked PERFECTLY! For me No Fog=No Stress.

4) Get a Wetsuit!!! A Wetsuit won't save you if you can't swim to begin with, but in my case, any anxieties I may have had about the swim were totally erased after my first OWS with a wetsuit. I felt like a friggin' cork bobbing in the lake, and with my fog-free goggles I felt like I could challenge Michael Phelps!...well, maybe that's a bit of an exaggeration, but my confidence went up ten-fold. I borrowed the wetsuit for the race and am currently waiting for one to arrive in the mail so I can keep lake swimming 'til it gets too cold.

Good Luck with your swimming!