I found a special rope that I use for outdoor training, and water training - it floats, the one i got was 30 ft long but they have it in the 50' too. I got mine on-line at
http://www.erinsedge.zoovy.com/product/MEN003SUPER This site has a lot of great stuff too...for all breeds ( they specialize in labs)
The rope may be a bit much for a small puppy...but great for training to swim and such...I will be using it attached to Dillon's collar in the kayak ( he has a life vest too) and that way if he jumps out ( doubt he will) he wont wash away ! I have a life line to drag him back ...
Emilie