According to GPT3:

Here are the steps that Muun wallet takes when using submarine swaps to perform a Lightning transaction:

The user initiates a submarine swap by specifying the amount of Bitcoin that they want to exchange and the address to which they want to receive the other cryptocurrency.

Muun creates a payment channel on the Lightning Network and sends an invoice to the user for the amount of Bitcoin specified in the submarine swap.

The user pays the invoice using their Muun wallet, sending the specified amount of Bitcoin to Muun through the payment channel.

Once the payment has been received, Muun sends the other cryptocurrency to the address specified by the user.

Both parties confirm the receipt of their respective funds, and the submarine swap is complete.

The transaction is recorded on the relevant blockchains, updating the chain history for both cryptocurrencies involved in the swap.

It's worth noting that this is a simplified version of the process, and there may be additional steps involved depending on the specific details of the submarine swap. However, these are the general steps that Muun follows when performing a submarine swap using the Lightning Network.