I’m new and clueless
Firstly check your swim distance is 750m - it's an unusual distance for a pool based sprint triathlon. Don't worry there will be other people mixing strokes - you won't be the only one. Don't worry about looking silly - we all do when we're clad in lycra - just enjoy it. If people catch up to you they will touch your toes and the etiquette is to let them pass when you get to end of the lane. Yes we wear trisuits in the pool too, not just for under wetsuits. Tumble turns are OK, unless strictly prohibited by your event organiser but they should tell you that in the pre-race briefing.
We were all beginners once and it's an inclusive sport. Just be aware of people who are faster than you and let them pass as described and you'll hve a great time.
Definitely do not worry about looking silly!
If it is the stroke you are most comfortable with to do the distance then stick with what you know you can succeed with.
Do not worry about what other people are doing in their races, and just focus on you and your performance.
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If you've made the swim distance you'll be fine. Im not sure on pool event, but in open water you can even stop and rest if need be as long as you are not making forward progress. Mixing up your strokes is fine as are tri suits. If in doubt check with the organisers.
The only thing you may find is that the adrenaline may grab you being around so many people in the pool. So it would be a good idea to swim with a friend and get them to swim behind you and touch your feet etc. Seems a bit weird but it will stop you getting startled in the water.
Swim tips...I'd focus on whatever stroke you want to adopt.
Over ten sessions you can build some good progressions in.
15 x 50m
10 x 75m
Have a great tri.