I was invited to join a couple groups who are doing the traditional 100 x 100 holiday workout tomorrow morning , but I had already committed to meet with the Wasatch Front Polar Bear Club for a Christmas Eve polar bear plunge. I've never done this workout before and I really wanted to try it, so I ended up doing it by myself at the pool this morning.
I chose an interval of 1:30 and made the first few on about 1:18. After that, I settled into a more normal pace and held 1:22 for quite a while. I dropped down to 1:24 to 1:25 near the end and finished with a sprint at 1:09.
I felt like my energy level was pretty good the whole way through and 2.5 hours went by really fast. Near the end my arms and shoulders were getting tired from swimming faster than usual, but I never felt like my stroke was falling apart.