what type of boat?

Hi all,
I recently started scratchbuilding some M4T6 pontoons (“floating bridge-system”) and the reason was this picture:

http://www.armorama.com/modules/photopost/showphoto.php?photo=60140&password=&sort=8&cat=500&page=1

I wanted to build this raft with the M4T6 pontoons and the quad 50’s but I can’t figure out what type of boat is pushing this raft in the picture (if you look closely you can see part of the bow between the pontoons, at least that’s what I think). I don’t think it is one of the boats normally used to push this floating bridge so does any of you have a suggestion?

Thanks in advance
Mark