How were "Aniyos Tarshish Sharosayich [Ma'aravech]"?
Rashi: They were for you an Aruvah 1 and a Mishor (a paved road to bring merchandise to a city on the land). So these boats were a path to bring your Aruvah into you. Sharosayich is an expression of Sharon 2 and Mishor, like "Alu b'Sharoseha" (Yirmeyah 5:10).
Radak: They were your Shayaros (caravans) going with your merchandise. I.e. many going together, like a caravan.
Malbim: All the boats were like Mesharesim (servants) to you. They were Arevim (guarantors) for you, for all of them were yours.
How will you be filled and very heavy?
Rashi: They will bring a great load into you; it will be too heavy.
Radak: This is like "v'Sarbi" (Yirmeyah 2:22 ? you will increase) and "b'Am Kaved' (Bamidbar 20:20 ? a huge nation).
Malbim: You became full of merchandise, and very honored.
Why does it say "b'Lev Yamim"?
Radak #1: It is as if you are in the middle of the seas, because boats come to you from all the seas.
Radak #2: It was built [on a rock] in the sea, like I explained (26:4). It says Yamim (plural) because this sea enters another, and so it says "ul'Mikve ha'Mayim Kara Yamim" (Bereishis 1:10).
