Pixie - I attended something similar down here and found it really useful - it was aimed around riding in a group so lots of drills to get you confident on the bike, track stands, picking up bike bottles off the floor whilst you ride past, hands on shoulders of the rider next to you, all really useful stuff and good fun.
Just got back from my 2nd swim of the week () hoping to turbo tonight, just found out my OH has organised a track taster session for me, the weekend after next, excited and a tiny bit scared, those bankings are steep.
Ali - according to my swim teacher it was hilarious. . . . anyway its because you tense your legs to grip the pull bouy they then just sway about, you have to learn how to maintain the grip on the PB without losing your body rotation, apparently its all about making sure your head position is good and using your trunk to fully rotate rather than relying on shoulders/hips. Stay strong from trunk to feet.
If you can't keep good body rotation PB work isn't useful because it can mean you stop the rotation when you are swimming without a PB.
This is only what I was told last night I haven't done any extensive research so I could be talking rubbish!
Swim last night, lots of resistance work to try and make me stronger, can see improvements but I did manage to almost swim backwards when using a pull bouy, my legs just swayed alarmingly from side to side and I didn't seem to go anywhere!