Two dead creatures and two kinds of blood have been made lawful for us, Jarad and fish, and liver and spleen.
أحلت لنا ميتتان ودمان: الجراد والحيتان، والكبد والطحال.
Bayhaqi (1/254) narrated it from the hadith of Ibn Wahb, who said, "Sulayman bin Bilal told us, from Zayd bin Aslam, from Abdullah bin Umar," and he mentioned it. Bayhaqi said, "This chain is sahih, and it carries the meaning of a musnad hadith." Ibn Abdul-Hadi likewise said in Tanqih (4/643), "The sahih version of this hadith is what Sulayman bin Bilal, the trustworthy and reliable narrator, related from Zayd bin Aslam, from Abdullah bin Umar, who said, 'Two kinds of dead animals have been made lawful for us.' This is mawquf but carries the status of marfu." Ibn Qayyim said in Zad Mad (3/392), "This hadith is hasan, and this mawquf report carries the status of a marfu one, because when a companion says, 'Such and such was made lawful for us' or 'was forbidden to us,' this is understood to refer to the Prophet's ﷺ ruling of lawfulness. It has been reported as marfu, but that is not sound. It was narrated by Ibn Majah (3218), Ahmad (5782), and Baghawi in his commentary (2803), all through routes from Abdul-Rahman bin Zayd bin Aslam, from his father, from Ibn Umar, who said, 'The Messenger of Allah ﷺ said,' and he mentioned the hadith. But Abdul-Rahman bin Zayd is daif." Imam Ahmad said, "He related a munkar hadith, the hadith 'Two kinds of dead animals and two kinds of blood have been made lawful for us.'" Aqeeli mentioned this (2/321).As for what was reported from Jabir bin Abdullah, who said, "The Messenger of Allah ﷺ said, 'Whatever the sea casts up or the tide leaves behind, eat it, but whatever dies in it and floats, do not eat it,'" this is problematic. It was narrated by Abu Dawud (3815) and Ibn Majah (3247) from Ahmad bin Abdah, who said, "Yahya bin Salim Taifi told us, Ismail bin Umaya told us, from Abu Zubayr, from Jabir," and he mentioned it. Abu Dawud said, "This hadith was narrated by Sufyan Thawri, Ayub, and Hammad, from Abu Zubayr, and they stopped it at Jabir as mawquf. It has also been related with a full chain reaching the Prophet through a weak route, from Ibn Abu Dhib, from Abu Zubayr, from Jabir, from the Prophet ﷺ."Bayhaqi related it through the route of Abu Dawud (9/255–256) and said, "Yahya bin Salim Taifi makes many errors and has weak memory, and others have related it from Ismail bin Umaya as mawquf." He perhaps means by "others" Ismail bin Ayyash, for Daraqutni related it (4716) through his route, from Ismail bin Umaya, from Abu Zubayr, from Jabir, that he heard him say, "Whatever the sea casts up, or whatever fish it uncovers, eat it, but whatever you find floating dead, do not eat it." Daraqutni said, "It is mawquf, and that is the sahih version."It has also been related through other routes as marfu, but all of them are problematic, and the sahih position is that it is mawquf. See Sunan Bayhaqi (9/256). As for fish that float dead, see the detailed discussion in Minna Kubra (8/278–279).