About a year or two after I adopted Maggie, my eldest, my ex and I took her and Guinness (then a puppy) to the lake behind our house. Now, before I get any further into the story, let me just say that Maggie dog is a PRISS. If it's cold, raining, snowing... if the lawn is so much as wet, she refuses to go outside to potty. She'll hold it until she can't hold it any longer. So we took her and Guinn out to the lake and I had an inflatable boat thingy. I blew it up and paddled out the middle of the lake. Little Maggie frantically paced back and forth at the shore for several minutes, whining, and eventually jumped into the lake and paddled out to me! About three quarters of the way she panicked and headed back for dry land, but it truly did seem like she was trying to "save" me!
I also think Guinness would and I think Frankie would. Total nanny dogs. The others? Romeo is too much of a wuss boy and Brooke-Lynn is too much of a doofus.