Boltz is a privacy-first account free exchange and a Lightning service provider. By doing a Submarine Swap on Boltz, you can swap your on-chain Bitcoin for Lightning Bitcoin.
Step 1: Deciding to Submarine Swap
You have one or more Lightning channels that are running low on outbound liquidity and you want to fund it using your on-chain Bitcoin.
Step 2: Sending the on-chain funds
You send the on-chain funds to an address which can only be spent by Boltz when it pays a Lightning invoice to your node.
Step 3: Receiving the funds on Lightning
Boltz pays the Lightning invoice to your node and claims the on-chain funds locked in the previous step.
Done!
You swapped your on-chain Bitcoin for Lightning Bitcoin, while also adding outbound capacity for your channels in the process - all in a non-custodial manner.