Generate a YGOPro Lua script for the following Yu-Gi-Oh card effect:
You can discard 1 other WATER monster to the GY; Special Summon this card from your hand. When Summoned this way: You can add 1 Level 4 or lower "Mermail" monster from your Deck to your hand. You can only use this effect of "Mermail Abyssteus" once per turn.
--水精鱗－ディニクアビス
--Mermail Abyssteus
local s,id=GetID()
function s.initial_effect(c)
	--special summon
	local e1=Effect.CreateEffect(c)
	e1:SetDescription(aux.Stringid(id,0))
	e1:SetCategory(CATEGORY_SPECIAL_SUMMON)
	e1:SetType(EFFECT_TYPE_IGNITION)
	e1:SetRange(LOCATION_HAND)
	e1:SetCost(s.spcost)
	e1:SetTarget(s.sptg)
	e1:SetOperation(s.spop)
	c:RegisterEffect(e1)
	--search
	local e2=Effect.CreateEffect(c)
	e2:SetDescription(aux.Stringid(id,1))
	e2:SetCategory(CATEGORY_TOHAND+CATEGORY_SEARCH)
	e2:SetType(EFFECT_TYPE_SINGLE+EFFECT_TYPE_TRIGGER_O)
	e2:SetCode(EVENT_SPSUMMON_SUCCESS)
	e2:SetCountLimit(1,id)
	e2:SetCondition(s.thcon)
	e2:SetTarget(s.thtg)
	e2:SetOperation(s.thop)
	c:RegisterEffect(e2)
end
s.listed_series={SET_MERMAIL}
function s.cfilter(c)
	return c:IsAttribute(ATTRIBUTE_WATER) and c:IsDiscardable() and c:IsAbleToGraveAsCost()
end
function s.spcost(e,tp,eg,ep,ev,re,r,rp,chk)
	if chk==0 then return Duel.IsExistingMatchingCard(s.cfilter,tp,LOCATION_HAND,0,1,e:GetHandler()) end
	Duel.DiscardHand(tp,s.cfilter,1,1,REASON_COST|REASON_DISCARD,e:GetHandler())
end
function s.sptg(e,tp,eg,ep,ev,re,r,rp,chk)
	if chk==0 then return Duel.GetLocationCount(tp,LOCATION_MZONE)>0
		and e:GetHandler():IsCanBeSpecialSummoned(e,0,tp,false,false) end
	Duel.SetOperationInfo(0,CATEGORY_SPECIAL_SUMMON,e:GetHandler(),1,0,0)
end
function s.spop(e,tp,eg,ep,ev,re,r,rp)
	local c=e:GetHandler()
	if not c:IsRelateToEffect(e) then return end
	Duel.SpecialSummon(c,1,tp,tp,false,false,POS_FACEUP)
end
function s.thcon(e,tp,eg,ep,ev,re,r,rp)
	return e:GetHandler():GetSummonType()==SUMMON_TYPE_SPECIAL+1
end
function s.thfilter(c)
	return c:IsSetCard(SET_MERMAIL) and c:IsLevelBelow(4) and c:IsAbleToHand()
end
function s.thtg(e,tp,eg,ep,ev,re,r,rp,chk)
	if chk==0 then return Duel.IsExistingMatchingCard(s.thfilter,tp,LOCATION_DECK,0,1,nil) end
	Duel.SetOperationInfo(0,CATEGORY_TOHAND,nil,1,tp,LOCATION_DECK)
end
function s.thop(e,tp,eg,ep,ev,re,r,rp)
	Duel.Hint(HINT_SELECTMSG,tp,HINTMSG_ATOHAND)
	local g=Duel.SelectMatchingCard(tp,s.thfilter,tp,LOCATION_DECK,0,1,1,nil)
	if #g>0 then
		Duel.SendtoHand(g,nil,REASON_EFFECT)
		Duel.ConfirmCards(1-tp,g)
	end
end