Dad was a Coastie, or rather is a retired Coastie. An unrelated search -- can I glean storage tips for a small apartment from the reality of shipboard berthing? -- led me to the US Coast Guard chaplain's page. I thought I'd point out two resources.
1. I found Coast Guard-themed prayers, the first of which is a glorious collect.
Almighty and Everlasting God, Whose hand stills the tumult of the deep, we offer our prayers for those who serve in our Coast Guard. We are mindful of their traditions of selfless service to the seafarers who make their ways to appointed ports. Employ their devotions of good ends as they track the weather and search for the seas for those in extremity of storm, shipwreck or battle. Make their soundings and markings sure that safe passages may be found by those who go down to the sea in ships. Encourage them, O Lord, as they stand guard over our coasts and the bulwarks of our freedoms. Graciously deliver them from threatening calamities in all their perilous voyages. Bless the keepers of the lights and be Thou their close friend in lonely watches. Keep the beacons of honor and duty burning that they may reach the home port with duty well performed, in service to Thee and our land. Amen.
Its tone suggests a moment of some occasion, say an Academy commencement, but in the civilian world that would have to be praying godspeed to a member who has joined the Coast Guard or (God forbid) some kind of ongoing disaster involving Coast Guard personnel. Bookmark it here if you think you might ever need it or any of the others, the rest being (well) less momentous and including graces.
2. There is also a USCG FAQ page that answers who qualifies for their services to be buried at sea. (Both of my parents would qualify, so I bet it quite a few, especially if you're in a coastal church or near a military base.) It doesn't say if there's a fee or if the remains must first be cremated, but another to resource to keep handy.
Frequently Asked Questions (US Coast Guard) At the bottom of the page; note the link to US Navy Office of Information page does not work.