Yes, you can scatter ashes at sea. This is much more popular than burial at sea because it’s less expensive and easier to do.
Scattering ashes at sea in the UK requires no licence or special permission. All you have to do is hire a boat, sail to a suitable spot and sprinkle the ashes on the water. Or, if you prefer, you can scatter the ashes from a beach or bury them in sand and let the water wash them away.
This might be a nice way to say goodbye to someone with a deep connection to the sea. It would be simple and inexpensive, but very poignant. Perhaps you could invite a few friends or family members to help scatter the ashes, then stand in silence as the waves lap peacefully around you.