Why not just do the 400m swim then you won't need fins, thus eliminating the ankle weights issue altogether...?
Actually there are several swims in total you have to do. 1- 15 minute treadwater, 2-400 swim, 3-800 snorkel, 4-100 diver tow. These are just the ones that require swim skills of some sort, other stuff you have to do all so. There are rules and times that have to met for each one of those. No substitutions and all have to be completed.
