MySQL synchronization

I have a cloud-based MySQL instance (slave) and am planning a solution where a remote instance (master) will be based on a ship. The ship will go in and out of international waters and therefore will have an intermittent terrestrial connection. When there is no connection, data will be stored locally. When the vessel arrives in an area with a terrestrial connection, I want the vessel database to synchronize with the cloud-based instance. This scenario will be duplicated with multiple vessels, with their own instances, and each vessel will need to send local changes to the cloud-based instance. We have looked at 3'rd party open-source tools like symmetric DS and wanted to 'ask-the-experts' the preferred approach. Is there a best-in-breed 3'rd party tool, or is the out-of-the-box MySQL solution sufficient? Thank you in advance.