Before going out at sea, recharge the battery of your SharkNet device. As you will see, SharkNet doesn’t have any plug: just put your device onto its wireless charging plate! The charge will definitely last the whole day!
Also, make sure that your subscription to SharkNet services is active. The subscription is needed to cover the costs of the phone connection of your device: you can activate it monthly (only when it’s needed) and, for a minimal amount, it allows your device to automatically connect with all the mobile networks of the world.
In any case, even if you forgot to check the status of the battery and of the subscription, don’t worry: the device will gently remind you flashing it light.