The Sea Monster has so many use cases when in battle. The monster is a tank with high health and a heal ability on top. With the heal ability already stacked on the monster with high attach and health, it makes a great pair with two other monsters.
Scavi Hireling and Meraali Guardian both offer another degree of protection for the Sea Monster. This leads to your tank surviving the majority of the battle and often times winning you the match. Scavo Hireling will restore a portion of the 1st monster's shield which protects the sea monster from your opponents tank, usually a high attach card. The Merdaali Guardian will heal the first monster on your team. This gives the Sea Monster DOUBLE heal!
These 3 cards have worked for me in multiple battles especially the relatively lower mana cap battles. I advise everyone to give it a shot. Please see below for a link of my latest battle where these 3 cards led me to a victory where the battle seemed lost.
https://splinterlands.com?p=battle&id=sl_d4ca4b63b0c29ed900084dae80153ade&ref=tscott