It doesn't matter if the target is moving. It doesn't matter if the water is moving. It doesn't matter if the platform the sniper is shooting from is moving. They'll hit because it's their job.

Marine Scout Snipers on mission with a Marine Expeditionary Unit conduct aerial sniping training from a rotary wing platform. This type of training is conducted to increase the skillsets of the individual Scout Snipers, which makes them a better asset for the Battalion Landing Team. At first glance, this may not seem like an incredibly important skillset for a Marine Sniper, who's job is primarily sitting in hides, providing intelligence to the Battalion Commander, and taking out targets of opportunity, but in a near-peer war this skillset is invaluable as it allows the Scout Sniper to integrate as part of the defense for the Marine Expeditionary Unit.