Lake Powell - two-way radio?

Bought a share on a houseboat. Looking for some good two-way radios. From what I can tell, there are no real good portable handhelds that go more than 5 miles without really good line of sight. That's not Lake Powell. So I am wondering if anyone that goes there can point me in the right direction. I ultimately want to be able to talk with the houseboat while it is anchored in a cove 20+ miles from Wahweap. If we go for supplies, I would like to be able to talk to the houseboat. Would a CB work or am I stuck with trying to get a ham radio?