Just browsing pumps. Looks like any of the 1/2 hp self priming centrifugal pumps would be more than adequate. May need a foot valve on some. I didn't look at any Chinese stuff wink

I would go with mag drive for reliability. Here's an example: http://www.iwakiamerica.com/products/SMX.htm

I'm not suggesting you buy this, it's just an example.

You could also hang a submersible pump off your dock, but you'll need one that has a continuous duty cycle (means it can run 100% of the time) They do make submersible pumps for Aquaculture/Irrigation that you can just drop in a river or lake, but they are a bit pricy.

What I would do here is too complicated for a short term setup. If it's gonna run for years and needs to be as energy efficient as possible as well as reliable, then I have other considerations.

Sounds like fun tho!