Jim Morash wrote:
"It will be tough to get the antenna more than a foot (maybe two) out of
the water."

It may be worth the effort for the sake of your hardware.

Distance to the horizon in miles is the square root of teice the antenna
elevation in feet.
Two feet elevation puts the horizon at two miles. 20 feet slevation on
the other end of your path extends it by 6 miles. Low obstructions may
block a very low path at times as 900 MHz requires a line-of-sight path.
You might anchor a buoy to hold your antenna at a convenient height.

A 1/2-wave coaxial dipole works about as well as any VHF or UHF antenna
on a boat or float. Commercial versions use 1/4-wave of rigid tubing as
a skirt over the coax feedline. This tubing is the lower half of the
antenna. The upper half is a 1/4-wave whip mounted on the lower half.
There are no radials to get in the way or poke out any eyes.

Best regards, Richard Harrison, KB5WZI