Cubozoa

Whoa!  That made a huge difference.  The Box Jellyfish are the fastest jellyfish by far, able to swim a metre in as little as ten seconds when going long distance, or sprinting short distances at a rate of a metre in half a second - around human walking pace.  When you are hunting small prawns and fish, that's plenty fast enough as they tend to hide rather than flee, and then your long tentacles can reach in and sting them.

Your tentacles increase in length and venom, and you become a pretty amazing hunting machine.  Some of you grow up to two metres across and three metres long!  

You develop two kinds of eyes, some of which are 'full' eyes, giving you 360 degree vision all around you (and in the ocean, that means above and below, too), as well as many more simple eyes that show only dark and light, which are perfect for spotting nearby prey movements.

You appear to have developed a full vision system, shown by your ability to swim towards and away from objects of interest or danger, and swim around obstacles before you can touch them.  This indicates some kind of awareness, even intelligence.  That's amazing!

That's as far as you can evolve here!  
You can go back to the start with the link above, or share what you became with the icons below.