Dave, N3WTK wrote:
"What suggestions have you for an antenna?"

Avoid the sharks off Cocos Island.

From a boat at sea, you have a perfect earth connection available. Dunk
an electrode and use it for HF. If the boat is metal, just make a ground
connection outside to the hull. HF won`t penetrate the metal. Then use a
vertical wire as an antenna. The sea short-circuits horizontal
polarization. L-antennas are often used on boats. The horizontal portion
is just capacitive loading for the real antenna which is the vertical
portion. Loaded vertical whips are another type of common boat antenna.

Best regards, Richard Harrison, KB5WZI