Certainly not a belly crawler or a sveni (check out old pictures of mine for C.saxatilis for pictures of my sveni before it was correctly ID'd) , i've had both and neither looks anything like that. C.sveni are members of the Saxatilis group and have characteristic white "spangles" all over the body which your fish doesnt have, bellycrawler are a very plain looking fish with no colour to the fins, they also have very poor swimming ability and stick to the substrate in an almost goby like fashion making short hops from spot to spot.
Judging by the body shape and long head i'd be more inclined to ID it as a juvinile of one of the Lugubris group of pikes that the Saxatilis or Reticulatus groups, unfortunately (or fortunately depending on how you look at it) these are the big boys of the pike world with all species growing to over a foot with ease.