Hi there...I am a 34DD and also do triathlons--so I have thought a lot about supportive sports bras!

I have the Enell bra, and have used it for 3 triathlons (2 Olympic, 1 sprint)--I haven't found anything that works better. You definitely can swim in it. (I called them to ask them, and they confirmed this.) True, it doesn't dry as fast as some of the most technical fabrics...so you feel wet for a while on the bike. But it is VERY supportive. On the other hand, it has so much compression that I don't really like working out in it...I feel too squeezed.

The best sports bra that I have found is by Champion: It is something like the Friction Free™ Seamless Full Support Sports Bra.

Most of the other ones out there don't have enough support--but let me know if you find something good!