Never seen anyone put them under not sure that would work. Those caps are so tight on the dome I can't image putting anything else in there except the dome.

Over the cap :)

Wow, thanks for the speedy replies!
I'd tried under a few times at the pool and it wasn't working out too well (cap sliding off etc.) so I'm glad I checked this out.

I wear mine under - it actually keeps them from getting knocked off. When you get hit in the face (not if, when) the goggles won't come off your head as the cap holds them in place. They may move on your face a bit but no hunting for them in the washing machine of the swim start. Never had any issue with the cap going over the straps - especially if the cap is wet first.

Under. If they do get kicked there is no chance of them coming all the way off your head.

I wear my goggles under my cap. Like previous posters said, if a strong wave or an errant foot knocks them off my face, they remain secured to my head and I can just readjust them on my face.

I lost one pair of goggles to a strong wave and started wearing them under ever since.

Definitely under. If I lose my goggles, my contacts are going and then I'll need the help of a well trained dog to find my bike.

um not most. I was competitive and no one did then. I always wear mine over. If they are under and get pulled off/ddown then they will be all funky winkerbean under your cap and you dont want that. Easier to re-adjust if they are over.

Definately under. I got my goggles knocked off during a race and had to fish around for them. Ever since then I have worn them under and have never had a problem.

I say under is best for comps. Training I leave them over. If you have a problem of the cap coming off when te goggles are under try a cap, then goggles, then race cap. This is especially great when it is cold as it keeps you warmer.

Under...keeps em in place when you get elbowed in the face!

I do the same as Flip12 - Under for races, then if I wear a cap in training - short haircuts help with no cap - I usually have it over. But the only time I make a conscious effort at it is during races - and it's under. I can see why competitive swimmers (i.e events held in pools) may not do the 'under' thing - no one's going to kick it off of your face.

On the other hand, one could argue there's a hydrodynamic advantage if the straps are under the cap.

When I swam with a master's group even for pool events people were told to do under to avoid the goggles getting taken off by diving in.

I still do over though in training. Always think about under at races, but never actually have.

I do over while training in the pool and under in races too