I happened upon this version of the legend earlier today, I forgot who showed it to me first, but I hope you enjoy it. (As a disclaimer, I changed the spellings to better match the current orthography. I also translated this version more or less contextually, but tried to keep it as literal as possible.)
Tåftåf gi ega'an gi primet na hå'åni di primet ågua di Åbrit. På'go dumokko' i atdao gi fanmaigu'on-ña. Ha i'ina gi sumanlichan i fansågåyan Hågåtña. Hagas i lina'la' guihi na fansågåyan ti matulaika. Hå'åni di hå'åni mataiguiguihi ha' i lina'la' i Chamoru.
(Early in the morning on the first day of the first showers of April. The sun was just sprouting from its resting place. It shone from the West on the village of Hågåtña. Life there in the village didn't change. Day to day it was the Chamorro way of life.)
Ma'ålok na gi manmaloffan na hå'åni siha guåha un achaiguasguas måñåsåga guihi na fansågåyan gi Barion San Nicolas, hihut gi Minondo gi Saddok Hågåtña. Ma'ålok nu ini na achaigåsguås na guåha maisan gefpå'go yan masamai na på'go pålao'an ni mafa'na'an, Sirena.
(It's said that in a past time there were people living there in the San Nicolas neighborhood, near Minondo by the Hågåtña River. It's said that among those people there was a beautiful girl, she was especially beautiful, who was called Sirena.)
Un hå'åni tinago' as nånå-ña, "Sirena, Sirena, iha, hågå-hu. Kahulo' yan un tåftåfgui chumuli'i i pinigan."
(One day she was commanded by her mother, "Sirena, Sirena, daughter, my daughter. Get up so you can go early and get the charcoal.")
Annai på'gu para u dingu si Sirena iyasihaa, gof tinago' as nånå-ña na cha'ña u o'otatnon. Tinago' na u lachaddek ni pinigan. Lao ma'ålok na chatmatågo' si Sirena. Mofo'na i tinane'-ña, tåtåtte i inesge'-ña. Ya yanggen guåha matågo'-ña, fine'na sumugo' gi saddok ya ñumangu.
(When Sirena was just about to leave, her mother sternly commanded her that she should not dawdle. She was commanded to quickly get the charcoal. However, it's said that Sirena didn't take orders well. First came her own business, then her obedience followed. And when she received a command, she would first stop by the river and swim.)
Ayu na oga'an, hagas ninangga nu as nånå-ña. Maloffan åpmam i hinanao-ña ki håfa matågo'-ña. Annai ti måfåtto ha', måtto i minaipe-ña ya ilek-na, "Asi pudiera mohon na u fama'guihan."
(That morning, her mother had been waiting. Her trip was taking a great length of time for what she was commanded. When she didn't come, the mother became enraged and said, "I wish she would turn into a fish.")
Annai på'go ha sångan uhi, kakakalom i matlinan Sirena. Ha li'e' na gof chathinasso. Ha faisin "Mångge si Sirena?"
(When she had said that, Sirena's godmother was entering. She saw that the mother was extremely worried. She asked, "Where is Sirena?")
Ineppe', "Gaigi ta'lo gi saddok ya ohalara mohon na u fama'guihan. Yanggen i hanom muna'mamagof gue', ohala mohon na u sen såga ha' gi saddok!"
(The mother answered, "She's at the river again and I hope she turns into a fish. If the water makes her happy, then I wish she would just stay there in the river!")
Ha alulåyi umenta'lu i matlinan Sirena. Ilek-ña, "Put et amot di Di'os! Na'yo'åsi' hao! Na'maggem i sentimiento-mu! Håfa masusedi, masusedi! Lao guåha lokkue' iyoku nu guiya kumu saina. ya iyoku ni pine'lon Yu'os, eyu ti siña matulaika, gi ilu-ña påpa' guatu gi apuyå'-ña! Ayu na echong-ña yan empi' ti siña måfnas gi tataotao-ña!"
(The godmother hurried to intervene. She said, "For the love of God! Have some compassion! Calm your emotions! What has happened, has happened! However, I also own a part of her as an elder. And mine is given to me by God, that part you can't change, from her head down to her navel! That part of her cannot be erased!")
Annai på'gu maloffan uhi na inadingan, ñumañangu ha' si Sirena gi saddok. Lao guihi na momento, chumatguiya. Mumakkat i tataotao-ña ya ha alulåyi ñumangu guatu gi fanggo'tiyan. Ha kehago' i hinagon-ña ya umågang, "Ai nåna, matlaya sea." Annai ha atan påpa' i nao'ao hånom, ha li'e' na matulalaika i tataotao-ña. Lumuhan ya guse' ha hasso i matågo'-ña.
(When the conversation had just taken place, Sirena was still swimming in the river. However at that moment, she felt ill. Her body became heavy and she hurriedly swam to the bank. She tried to catch her breath and called out, "Oh Mother, matlaya sea*." When she looked down in the clear water, she saw her body was changing. She became frightened and quickly remembered what she was commanded.)
Guihi lokkue' na momento, manfugo' yan ha sienti na nana i makkat ya maipe na fino'-ña; lao atrasao. Ha falågue malak i Minondo. Annai ha li'e' si Sirena, ha tungo' na hiningok yan magutos i fino'-ña mågåhet. Kumasao ya ilek-ña, "Sirena, Sirena, hågå-hu, asi'i yo'ni fino'-hu. Na ada ennao mågåhit minalago'-hu!"
(Also at that moment, the mother shivered and felt how hard and hot her words were; but it was too late. She went running to Minondo. When she saw Sirena, she knew she was heard and her last words come true. She cried and said, "Sirena, Sirena, my daughter, forgive me what I said. It wasn't what I really wanted!")
Annai ha hihuhuti si Sirena, ha kehago' i kannai-ña, lao ti siña ha go'te.
(When Sirena came close, she tired to reach for her hand, but she couldn't hold it.)
Inatan hulo' gi fanggo'tiyan ya ilek-ña, "Nåna, masusedi, åsi'i yo'. Håfa maloffan, maloffan."
(She looked up at the bank and said, "Mother, it's already done, forgive me. What has happened, has happened.")
Annai på'go ha sångan uhi, milalak i lago'-ña ya ilek-ña, "Nåna, adios, adios, nåna. Yo entrego mi alma**."
When she has said that, her tears flowed and she said, "Mother, goodbye, goodbye, mother. Yo entrego mi alma.")
Ma'ålok na desdi ayu na hå'åni, sumåga si Sirena gi pachot Sågua' Hågåtña. Tåya' na ma li'e'. Lao i fumatotoigui yuhi na lugåt, ma'ålok na ma huhungok i masamai na lailai-ña.
(It's said that from that day, Sirena stays at the mother of the Hågåtña River. They never see her. However, those that come by that place, it's said that they hear her song.)
*I don't really know what "matlaya sea" means.
**Spanish for "I give my soul."