GFCIs fail. Pond pumps are certified to a much higher standard than the "lake pumps" I see around here, which are almost always shallow well pumps with DIY electrical service.
OP said he was going to put the pump on the dock. A few feet from the water's edge may be an OK safety margin. Personally I wouldn't want anyone to be able to reach it while touching the water in any way.
When I put my pump in next year the most convenient place is for it to be housed and sheltered in a wood shed 10' from the shore so that's where it will be. I'll put it on a GFCI and if it fails someday the hazard will still be 10' from the water and in a dry area.
To the OP, I'd suggest you check local electrical code. Stay safe.