New and Mostly Clueless

Hello everyone! I'm fairly new to the RC scene and I'm looking to create my first boat. I'm 3d printing a few different models from Thingiverse.com right now, but haven't decided it's final form yet. I have extensive 3d printing knowledge, so the actually construction and seaworthiness isn't what I need help with - rather, what to put in as far as electronics.

Here's my dream, and I was wondering if I could borrow some of your collective expertise:

For some reason, the idea of having a little RC tug boat to bring my friends seltzers on the lake brings me a lot of joy. It doesn't need to be fast but I'd like it to last longer than 15 minutes before needing to be recharged.

I'd like it to be primarily solar, as Lipo batteries scare me - but there's very few projects out there that show successful solar boats with RC control and steering. I imagine I'll need a rechargeable battery working in tandem with the solar cells.

It doesn't need to be fast, or crazy powerful. The emphasis would be on efficiency and longevity. The frame will probably be no longer than 350mm. I was thinking of having it pull a tiny drink inner tube, since I feel like having a beer on the actual boat would throw off the balance too much.

I'm having a hard time deciding how powerful of a motor and approximately how much power overall I would need.

Any suggestions, tips, or resources would be beyond appreciated.

Thank you! I'll be sure to post updates about the SS SeltzyTug.