The Prophet ﷺ said, "The seasick person at sea who is overcome by vomiting receives the reward of a martyr, and the one who drowns receives the reward of two martyrs."
عن النبي ﷺ أنه قال: المائد في البحر الذي يصيبه القيء له أجر شهيد، والغرق له أجر شهيدين.
Abu Dawud (2494) and Ibn Abu Asim in Jihad (285-286) narrated it through various chains from Marwan bin Muawiya, who said, Hilal bin Maymun Ramli narrated to us, from Abu Thabit Yaala bin Shaddad, from Umm Haram, and he mentioned it. Its chain is hasan because of Hilal bin Maymun Ramli, for he is hasan al-hadith.As for what has been narrated from Abu Darda that the Messenger of Allah ﷺ said, "A military expedition at sea is equal to ten expeditions on land, and one who is tossed about at sea is like one wallowing in his blood in the path of Allah," its chain is daif. Ibn Majah (2777) narrated it from Hisham bin Ammar, who said, Baqiya narrated to us, from Muawiya bin Yahya, from Layth bin Abu Salim, from Yahya bin Abbad, from Umm Darda, from Abu Darda, and he mentioned it. Its chain is daif due to the weakness of Layth and Muawiya bin Yahya (who is Sadafi), and due to Baqiya bin Walid's use of an ambiguous transmission formula, for he used to conceal his transmission from weak and unknown narrators. Busiri said in Misbah Zujaja (3/159), "This chain is daif due to the weakness of Muawiya bin Yahya and his teacher Layth bin Abu Salim." His saying "yasdur" comes from sadr with a vowel, meaning dizziness, which frequently afflicts one who rides upon the sea.Likewise, what has been narrated from Abu Umama is not sahih. He said, I heard the Messenger of Allah ﷺ say, "A martyr at sea is equal to two martyrs on land, and one who is seasick at sea is like one wallowing in his blood on land. And what lies between two waves is like devoting one's entire life to obedience to Allah. Allah has entrusted the angel of death with taking souls, except for the martyr of the sea, for he himself takes charge of taking their souls. The martyr of the land is forgiven all sins except debt, but the martyr of the sea is forgiven both sins and debt." Ibn Majah (2778) and Tabarani in Kabir (8/200) narrated it through the route of Qays bin Muhammad Kindi, who said, Ufayr bin Madan Shami narrated to us, from Salim bin Amir, who said, I heard Abu Umama say, and he mentioned it.In this chain is Ufayr bin Madan, who is daif. In fact, Abu Hatim said about him, "He is daif al-hadith, and he narrates extensively from Salim bin Amir, from Abu Umama, from the Prophet ﷺ, reports that are objectionable and have no basis, one should not concern oneself with narrating from him." Jarh wa Tadil (7/36). Busiri also faulted this chain for the same reason in Misbah Zujaja (3/159). Qays bin Muhammad, who is Ibn Imran Kindi, has not been declared reliable by anyone except that Ibn Hibban mentioned him among his trustworthy narrators (9/15) and said, "His narration is to be considered when it is not through his transmission from Ufayr bin Madan."Likewise, what has been narrated from Abdullah bin Amr as a marfu narration is not sahih, "No one should ride the sea except a pilgrim performing hajj, or one performing umrah, or one waging jihad in the path of Allah, for beneath the sea is a fire, and beneath the fire is a sea." Abu Dawud (2489) narrated it from Saeed bin Mansur (and it is in his Sunan, 2393), who said, Ismail bin Zakariya narrated to us, from Mutarrif, from Bishr Abu Abdullah, from Bashir bin Muslim, from Abdullah bin Amr, and he mentioned it.In its chain are Bishr Abu Abdullah and Bashir bin Muslim, both unknown narrators. There has also been disagreement over its chain. Some narrated it in this manner, some dropped Bishr Abu Abdullah, some dropped Bashir bin Muslim, and some narrated it in other forms altogether. Bukhari traced this disagreement in Tarikh al-Kabir (2/104-105), as did Khatib in Talkhis Mutashabih (1/156-158), and Mizzi in Tuhfat Ashraf (6/282). More than one scholar has declared this hadith daif. Bukhari said, in his entry on Muslim bin Bashir Kindi in Tarikh al-Kabir (2/104-105), after tracing the disagreement in the chain of the aforementioned hadith, "His hadith is not sahih." Ibn Abdul-Barr said in Tamhid (1/240), "It is a daif hadith with an obscure chain that the scholars of hadith do not consider sahih, because its narrators are unknown and not recognized..." It also contradicts some sahih hadiths. Ibn Hajar said in Talkhis (2/221), after tracing the statements of the scholars regarding the weakening of this hadith, "This hadith is contradicted by the hadith of Abu Hurairah... regarding the fishermen's question, 'We ride the sea and carry with us only a small amount of water,' and he did not object to what they were doing."However, this has been established as a stopped statement (mawquf) from the words of Abdullah bin Amr bin As. Bayhaqi (4/334) narrated, through the route of Shuba and Hammam, from Qatada, from Abu Ayub (who is Maraghi), from Abdullah bin Amr, that he said, "Sea water is not sufficient for wudu or for major ritual impurity, for beneath the sea is a fire, then water, then a fire," until he counted seven seas and seven fires. Its chain is sahih.