Due to the previous ruling of "Poison Draw Frog" with "Relinquished", when it is equipped to this card it still has its effect and thus every time you send a "Poison Draw Frog" equipped to "Sea Lancer" to the Graveyard to protect "Sea Lancer" you also get a free draw. With 3 copies of "Poison Draw Frog" you get 3 free draws every time you summon "Sea Lancer". (This also works with the effect of "Dupe Frog", allowing you to search a "Frog" monster instead of drawing.)
Other interesting cards to equip to "Sea Lancer" include "Oyster Meister" (to get his effect when sent to the Graveyard). "Oyster Meister" can produce a token that can serve as a substitute for "Treeborn Frog", as it can't summon itself when "Sea Lancer" is equipped with monsters.
Additionally, equip Dupe Frog to nab a Frog monster when this card would be destroyed.
Discard a "Frog" Monster to Special Summon "Swap Frog", then send "Ronintoadin" to the Graveyard. Use "Swap Frog's" effect to return itself to your hand. Activate "Ronintoadin" by banishing the monster you discarded and Special Summon it, then tribute it for "Sea Lancer". You can now equip the monster you just banished.