The soft V neck on the Laminaria Swimsuit is really easy to sew and gives you results that are almost as nice as the sharp V neck, so if you’re not looking to give yourself an extra challenge, this is the way to go.
Cut your elastic to the length described in the instructions. Mark the center of the elastic with a pen. You can go ahead and write with a ball-point pen or permanent marker (instead of a wash-away marker) since it won’t be seen in the finished suit.
Pin the elastic to the inside of the suit. I like to use pins horizontally so I can take them out as I sew. The elastic is the same length as the fabric here so no need to stretch or gather anything. Make sure that your center mark aligns with the center of the V. The exact position of the ends of the elastic (whether they abut or overlap the side elastic) doesn’t matter since the point will be cut off when we attach the straps.
Sew the elastic to the top of the suit using a zig-zag stitch. This is easy to do along most of the V although you might find it a little difficult at the point of the V since the elastic wants to go in a smooth curve but the fabric comes to a point. It’s okay if your elastic doesn’t sit exactly on the edge of the fabric as long as it’s close. You can see below that my elastic peeked up a tiny bit in the very middle.
Attach the straps as described in the instructions.
Then flip the elastic to the inside and sew it down. When the suit is lying flat it’s not quite as elegant as the sharp V neck, but once it stretches out as you put it on, it will look smooth.
Voila! The soft V neck.
For comparison, this is the sharp v neck. (This green suit is a little bit longer with straps that are a little bit shorter so the V is hitting my chest in a slightly different place).