In the name of Allah, We praise Him, seek His help and ask for His forgiveness. Whoever Allah guides none can misguide, and whoever He allows to fall astray, none can guide them aright. We bear witness that there is none worthy of worship but Allah Alone, and we bear witness that Muhammad (saws) is His slave-servant and the seal of His Messengers.
Allah says in the Holy Quran Chapter 16 Surah Nahl verse 14:
It is He (Allah) Who has subjected the sea to your service so that you may get fresh flesh from it to eat and bring out of it articles of ornaments,  which you wear.
Sunan of Abu-Dawood Hadith 83Â Â Â Â Â Narrated by Abu Hurayrah
A man asked the Messenger of Allah (saws): ‘O Messenger of Allah (saws), we travel on the sea and take a small quantity of water with us. If we use this for ablution, we would suffer from thirst. Can we perform ablution with sea water?’ The Messenger of Allah (saws) replied: ‘Its water is pure and (even) what dies in it is lawful food.’
Sahih Al-Bukhari Hadith 5.648Â Â Â Â Â Â Â Â Â Narrated by Jabir
We set out in the army of Al-Khabt and Abu Ubaida was the commander of the troops. We were struck with severe hunger and the sea threw out a dead fish the like of which we had never seen, and it was called Al-‘Anbar.  We ate of it for half a month. Abu Ubaida took (and fixed) one of its bones and a rider passed underneath it (without touching it). (Jabir added:) Abu ‘Ubaida said (to us), “Eat (of that fish).”   When we arrived at Medina, we informed the Prophet (saws) about that, and he said, “Eat, for it is food Allah has brought out for you, and feed us if you have some of it.”  So some of them gave him (of that fish) and he (saws) ate it.
In light of the above clear guidance of Allah and His Messenger (saws), the absolute majority of the eminent scholars and jurists in Islam are of the opinion that the flesh of every animal, without exception, that predominantly lives in the sea would be absolutely ‘halaal’ for the believers to consume.
Because there are a few restrictions and prohibitions amongst the animals of the land and air, it would only be prudent for the believers to determine whether the flesh of the animal of the land or air they are about to consume is lawful or not…..but when it comes to any food from amongst the vegetation or the sea….absolutely everything is assumed lawful and thus the need does not arise to ascertain whether a particular type of food from amongst the vegetation or the sea is lawful or not.
Whatever written of Truth and benefit is only due to Allah’s Assistance and Guidance, and whatever of error is of me alone.  Allah Alone Knows Best and He is the Only Source of Strength.
Your brother and well wisher in Islam,
Burhan