Crumm, as soon as I read that you're cutting trees out of a boat I thought of the only time I've cut trees out of a boat...on a moose hunt! Then I looked at where you're from and bingo!!
While all very knowledgable, I'd reckon that most of the responders thus far haven't been on the Wood River floating their way down to the Tanana to get to their pull out at Nenana so they can drive up to the Monderosa and get a burger after two weeks on the river!
Skip the handsaw, and forget the pole saw. No way. You can go two ways. Get yourself something like a little Husky 55 Rancher with a 24" or a Stihl 026/260 with a 24", depending on what you want to spend. There's a Stihl dealer in Fairbanks isn't there? I thought there was. My buddy uses an old Homelite top handle XL2 or something with like an 18" bar on it. And it starts every time. Even after being dunked several times. The top handle configuration is nice because we float so the smaller saw fits in the raft well, and the top handle lets you one-hand out in front of you or off the side if need be. I'd put a lanyard with a quick disconnect on it to keep it with the boat, and also allow me to snap it off quickly so we can beach and run down river to clear a jam if need be. We never teathered the Homelite. It never occured to us!
Normally I wouldnt' recommend a 24" on a little saw like that, but you aren't cutting timber or even cutting for any length of time. We've actually done well witht the 18", as it was less unweildy, and we're able to cut up even the largest logs enough to get the raft over them. Are you in an air boat or a jet drive?
So yeah, it's dangerous using a saw while hanging out of a boat, but no more dangerouse than to be there and getting stuck in a log jam without a saw and getting sucked underneath it, only to be found at ice-out. So all the "this is very dangerous" advice is good, but it doesn't apply here, so I don't have to tell you handsaw and polesaw options aren't viable.
How's the winter been? Do you have your name in the hat for Nenana ice-out?
Take care my brother!
Jeff