My thinking is that "on a moving vessel / boat" the most important point is getting a consistent signal higher than the minimum Outernet receiver threshold. Lets say minimum reception is 3 Units.
If the patch antenna is laid horizontally flat, pointing up, and works fine on flat water that's fine . But when a boat starts to move The patch antenna will move towards the satellite but also swing away from it. If the receive pattern at this point is less than three units of reception signal we loose packets. (Lost packets may be corrected by FEC)
My understanding is a short Helix antenna with a ground plane plate / reflector attached will have a hemispherical reception pattern. As a boat moves it should receive a satisfactory signal as it changes angle to the satellite.
This is the type of Antenna Inmarsat has been selling for their L-Band Maritime Emergency Low speed data service.
The Global Maritime Distress and Safety System (GMDSS)
"Inmarsat B is a digital mobile satellite communication system providing two-way direct-dial voice, telex, fax and data communications at rates up to 9.6kbps, anywhere in the world outside of the Polar Regions."